It appears the 2.6.20 version of the Linux kernel about to be release will include a lot of PS3 enhancements.
According to this page the changes are made by Sony engineers.
Found from a this Slashdot post.
Here is a softpedia article on it.
Where Linux geeks and lovers come to learn, play, and experience life with the Play Station 3! Key topics include installing your favorite OSS, running MythTV, and fun PS3 Linux tricks.