I just finished a program and a library to use an XBox 360 Chatpad as a Linux keyboard using the input sub-system. This means it acts exactly like a native keyboard and works with even framebuffer terminals. I’ve used it on my laptop with a USB serial adapter and on a Raspberry Pi.
Usage and more details can be found on the Github page here: https://github.com/timstableford/chatpad-linux
Just as a warning for some reason one of my USB serial adapters didn’t work properly with the keyboard and I had to try another.