Outsiders of the group of developers regularly complain that it's very hard to get an understanding of what happens in development of the Radeon driver(s). They have convinced me.
So I've spent some time to refactor the documentation on the DRI Wiki, creating a new, cleanup up and up-to-date portal page in the process. However, this refactoring is not complete, and the amount of information is not yet entirely satisfying. The real test now is whether this can be more than a one-shot effort by me, so this is a shout out to others - particularly to the users who have been asking for this - to help improve the documentation.
Partly, this can be done in very mundane ways by normal users. The application support matrix needs to be updated for Mesa 7.6 (there have been a lot of significant improvements), which mostly requires testing by a lot of people who own the necessary hardware/software combinations.
I have also created a stub page for 3D troubleshooting and known problems, and I want to rely mostly on users to help filling that with useful information. After all, the kind of trouble I run into usually has to do with me breaking the driver during development, which is on a rather different level from the kind of trouble users run into.
Now my main goal is actually to improve the way we present ourselves to potential new developers. This is also quite tricky because after having been immersed in this stuff for so long, it is hard for me to judge what kind of information and documentation would be most helpful to newcomers. If you have a concrete question, or set of questions, I'd be curious to know, and I may end up blogging on it, or documenting it on the Wiki, or documenting it in the source code. However, please give me more than a muddy "this stuff is complicated, can you hold my hand through it?", because yes, unfortunately, this stuff is complicated.
In my experience, the first step to understanding the 3D driver is to understand OpenGL. After all, the purpose of the 3D driver is ultimately to implement an API - and you just won't understand the driver if you don't understand that API. So if you're curious about 3D driver development, hack on little OpenGL samples first, or even at the same time! It doesn't have to be a large game engine; the samples that come with Mesa may be more than enough as a starting point. Then maybe you want to step through your program and what the driver does in a debugger, or experiment with other little ways that can help you understand the driver.
I hope that we will be able to welcome you into the fold one day.