I created compat-drm git tree on GitHub. This is a cleaned and stripped version of compat-wireless tree with some initial work done for building drm drivers. I’m currently working on building the latest linux-next drm drivers on kernel version 3.4 and sending the backport patches regularly to my mentor Luis Rodriguez and to the linux-wireless mailing list.
If you have to dig into kernel maintenance and building, I strongly suggest you to take a look at the kbuild documentation available in the linux kernel tree. It reveals a lot of things about building kernel and modules.
Stay tuned for updates.