The Android drivers were no longer accepted in the mainline Linux kernel, starting with Linux kernel 2.6.33, as announced by Greg Kroah-Hartman back in spring 2010.
But this is about to change, as it appears that Greg Kroah-Hartman will include the Android drivers into his development branch for the upcoming Linux kernel 3.3, making it boot on Android devices without being patched.
The Linux Foundation’s Consumer Electronics workgroup, along with a group at Linaro and various individual developers, is working with Kroah-Hartmann on this project. Tim Bird, chair of the Architecture Group, announced the Android Mainlining Project on the 20th of December with the goal of coordinating work on integrating the Android features. Further information on this project is available on the wiki and developers can also sign up for the project’s mailing list to join the 15 other persons involved in the project.