Afatech AF9015 COFDM demodulator IC.
This chip is the main USB control/demux in some cheap usb DVB-T dongles currently available. My dongle is the WandTV.
I'm currently writing a driver for this chip, though it might be worth documenting the process as there's not much around in terms of a howto in the subject.
I've got a head start in that there is an earlier chip from Afatech that's recently had drivers written for it, the AF9005. I've got the drivers for that chip along with the documentation for that and my chip, so I'm going to be working on modifying the AF9005 drivers to work on my chip. I'm not sure if I'm allowed to post the documentations here, I'll find out and if so a link will be posted.
To start with, there are some great Linux USB tutorials on Linux Journal: start here:
http://www.linuxjournal.com/article/4786 (How to Write a Linux USB Device Driver)
then here: http://www.linuxjournal.com/article/7353 (Writing a Simple USB Driver)
http://www.linuxjournal.com/article/5604 (Hot Plug)
and then: http://www.linuxjournal.com/article/7582 (Snooping the USB Data Stream)
also get the source for V4L-DVB: http://www.linuxtv.org/repo/ download using mercurual.
Then the usb drivers are in ./v4l-dvb/linux/drivers/media/dvb/dvb-usb Have a bit of a browse through them while you're reading through the first article above, get a feel for how the driver is put together. (There is a procedure described in http://www.ubuntuforums.org/showthread.php?p=1067326)