USB Wireless device support

[Bastien Nocera]

Hey,

I've recently bought a SteelSeries Arctis 1 wireless headset:
https://steelseries.com/gaming-headsets/arctis-1-wireless-xbox
and wanted to write a kernel driver to export a few features of the
device, and needed some help getting started.

The receiver shows up as a audio class USB device, with extra features
on a separate USB interface.[1]

The extra features that can be accessed are:
- Presence detection. I wanted to use that so PulseAudio or Pipewire
could make routing decisions based on whether the headset is available,
or probably better, implementing a "jack detection" emulation for the
main audio interface?
- A slider to change the sidetone volume
- Export the battery level

The latter is the only one I know how to do, so I'd be happy with any
pointers or examples about the first two items.

Cheers

[1]: User-space code that accesses those features:
https://github.com/Sapd/HeadsetControl/blob/master/src/devices/steelseries_arctis_1_xbox.c