j-g-

This is really weird, try to see if udev report any error, run as root 'udevadm monitor' and plug the device, and watch the contents of /proc/net/dev and /proc/net/wireless, I don't think the problem is the kernel, but can try using sys-kernel/gentoo-sources, and use iwconfig from wireless-tools, and ip from iproute2, instead of ifconfig, there might be a bug that's causing this, in which case I can only help you find out what is causing it, it's up to you to report it to the proper people.

At least we know now the kernel is detecting it, What's the output of 'rfkill list' is phy0 blocked?
 
PD: If you ever need to troubleshoot a wireless adapter again, go from bottom to top in this thread, we did it all backwards haha, sorry for that. I really thought from the beginning you didn't even had your driver compiled.

This is starting to sound like a firmware problem, you should have then the module rt3573 in /lib/modules/${kernel_version}/, search with `find` in that directory for "rt3573*" just  to confirm the *.ko file exist, if is there try to load it, if still nothing, this might be a firmware problem, do you have sys-kernel/linux-firmware installed in your system? I had a problem with firmware not being available to load for a Linksys card too some time ago(I just recalled this, though that was in debian).

What kernel version are you using? 
You should also search the specific firmware you need and check it is in /lib/firmware, and boot the kernel to test.
 
I found that blog, when I googled a bit about your device, but it's from 2012, and things have changed since, don't try it, you won't  even find the file it's said to edit, anyway a couple of "grep -rin" inside drivers/net/wireless/rt2x00/, in the kernel sources, got me to:
drivers/net/wireless/rt2x00/rt2800usb.c, see line 1216, your device its already there.
 
 
 
As previously said I'm running a 3.15.* gentoo-sources kernel.
Since its a usb device, try when running funtoo(not in chroot), run dmesg without the device, imediatly plug it in, run dmesg again, and see what happened, or post it here.
EDIT: I enabled the options you need in my kernel config, basically RT2x00, RT2800USB, RT2800USB_RT3573, and build a tarball, then looking at the drivers built here is a list of the relevant files, created:
kernel/drivers/net/wireless/rt2x00/rt2x00lib.ko
kernel/drivers/net/wireless/rt2x00/rt2x00usb.ko
kernel/drivers/net/wireless/rt2x00/rt2800usb.ko
kernel/drivers/net/wireless/rt2x00/rt2800lib.ko
 
So what you need to load is rt2800usb, not rt3573 nor rt3573sta as we were thinking.

You don't need to boot other OS in order to get a new driver, you should already have the kernel source code on your system, first find out which driver supports your device(google might help you with that) and the name of the kernel configuration variable that enables it, should be something like 'CONFIG_YOURMODULE', then verify its compiled and supported for the specific kernel version you are using, if your hardware is new you might need the latests version you can get.
modprobe 'module_name'
If  you don't have it,  you can compile it you just need to enable it in your kernel .config, rebuild and reinstall, no need to reboot if you build it as a module and not inside the kernel image.
If you need further help post the hardware model and version, and your kernel configuration.

If you haven't found out yet you need, to enable 'CONFIG_RT2800PCI_RT35XX' to build it, see [1], the easiest way is to run 'make menuconfig' on your kernel source directory, and use '/' and search for 'RT2800PCI_RT35XX', or go:


I'm running a 3.15.3 gentoo-sources kernel, and when I searched with menuconfig, this particular config was marked as 'EXPERIMENTAL', so it seems like recently added, make sure it is actually supported if you're planning to run an older kernel.
 
[1] http://cateee.net/lkddb/web-lkddb/RT2800USB.html

I didn't compile the default funtoo kernel, but I bet it has CONFIG_IKCONFIG enabled, so look for /proc/config.gz and copy it anywhere, as a backup of your current kernel, if you are going to use the same version you can try building a new configuration to use with genkernel, if you already have the source under /usr/src/linux, you might do something as follows:
# zcat /proc/config.gz > /usr/src/linux/.config # cd /usr/src/linux # make menuconfig Using '/' you can get a search dialog, and you can search for 'RT2800PCI_RT35XX'.
You'll get something like this:
 Symbol: RT2800PCI_RT35XX [=y]                                                                                                                              Type  : boolean                                                                                                                                            Prompt: rt2800pci - Include support for rt35xx devices (EXPERIMENTAL)                                                                                        Location:                                                                                                                                                    -> Device Drivers                                                                                                                                            -> Network device support (NETDEVICES [=y])                                                                                                                  -> Wireless LAN (WLAN [=y])                                                                                                                                  -> Ralink driver support (RT2X00 [=m])                                                                                                           (1)         -> Ralink rt27xx/rt28xx/rt30xx (PCI/PCIe/PCMCIA) support (RT2800PCI [=m])                                                                        Defined at drivers/net/wireless/rt2x00/Kconfig:87                                                                                                          Depends on: NETDEVICES [=y] && WLAN [=y] && RT2X00 [=m] && RT2800PCI [=m]                                                                               you can hit '1' (or if you got more options the number you want) and it will take right to the config section, if you have the Dependencies already enabled, Notice:
Depends on: NETDEVICES [=y] && WLAN [=y] && RT2X00 [=m] && RT2800PCI [=m] I Had to enable first those, to be able to see 'CONFIG_RT2800PCI_RT35XX', in my case(I build a only-what-i-need kernel) so my desktop had wireless completely disabled, I don't think that is your case, but, make sure the dependecies for the module you are building are enabled , in this case the last three if you notice  above are in the location in cascade, so if you navigate through menuconfig when you enable CONFIG_WLAN you get a submenu where CONFIG_RT2X00 is available, as 'Ralink driver support' :
... < > Softmac Prism54 support <M> Ralink driver support ---> < > Realtek rtlwifi family of devices ---- [ ] TI Wireless LAN support ---- ... And in there is what you need, you can also change 'CONFIG_LOCALVERSION' to something you like, so your anything you have now stays untouched(kernel-image and modules), when you finish save your config, you will be asked for a name, defaults to .config. Then recompile I've never used genkernel to build my kernels so I really don't know it but, funtoo wiki says this should do the work:
# genkernel --kernel-config=$YOUR_CONFIG_NAME all I hope this helps you, and give it a read at 'make help' in the kernel source directory, all the 'make *config' and building/packaging options are described there, if you are more curious unpack a kernel tarball under any directory you want as an unprivileged user copy your running config file as mentioned above to the as .config, run make menuconfig and start tweaking, you can even build binary tarballs of your  kernel image and modules with 'make tarxz-pkg' as an example before installing anything for real in your system.

This is not an error, this is portage telling you that php needs the 'sockets' USE flag enabled and this is required by cact. It is asking for your consent to pull dependencies you haven't explicitly requested, I have run in to portage asking me to do this several times.
You only need to do:

# echo '>=dev-lang/php-5.5.14:5.5 sockets' >> /etc/portage/package.use
and emerge -auvDN @world again.
PD: do as the output says too, and `man 5 portage` theres more about, package atoms and USE flags you should know, I'm sure you'll find some things nice you might want to use, portage is pretty awesome.

Read my edit, the bellow paragraph was out of ignorance, of the recent events.
I use systemd and I don't think this will affect eudev nor anything using dbus, anyway let's not turn this about it(systemd), I've been reading some about kdbus and from what I've read there will be a userspace daemon that will be a drop-in replacement for dbus but using kdbus in the background, anyway eudev pretty much is just getting udev outside of the systemd source code tree(search the git logs and see for yourself), for building it alone, and kdbus is an IPC system inside the kernel it isn't part of systemd, so you I think you are worrying about nothing in this particular case.

If you are not one of those people allergic to Lennart, here's a good video with *Technical* information about kdbus[1]
 
 
 
[1] https://www.youtube.com/watch?  v=NgR6d54blrU (join the space, the forum grabbed the video embedded with the complete URL)
 
Edit: I hadn't read your link, my bad, Well then there's things to worry about, for eudev, but I bet the the path will be to implement another kdbus userspace, but in my opinion while, this deafinitelly means a lot of work, it may not be a bad thing.