Android Kernel Download
Main Google Android Kernels
The main Google repository with Android source code is at: http://android.git.kernel.org/
There are (as of September 2009) 4 main separate kernel repositories at that site:
To download one of these and use it directly, you can use git. For example:
git clone git://android.git.kernel.org/kernel/common.git kernel
To preserve your sanity, it's probably worth downloading this into a 'kernel' directory in your overall Android source directory scheme
To add one of these to your overall Android repository scheme, you add the appropriate kernel repository to your local_manifest.xml file. (???)
Note that when you download the rest of the Android source code, using the 'repo' command, you do NOT automatically get a kernel tree included. (That is, a kernel git tree is not referenced in the default Android manifest file, when you use repo following the instructions at http://source.android.com/download
For more about repo, see http://source.android.com/download/using-repo
Other Repositories with Android-specific changes
- Linux kernel for omap and beagle-board, by Embinux: http://labs.embinux.org/git/cgit.cgi/repo/kernel.git
- clone with: git clone git://labs.embinux.org/repo/kernel.git kernel
'Raw' Android kernel patches
I do not know of any freely available patches for the Linux kernel with the Android fixes, as of November 2009. I have, however, heard of multiple efforts to extract the patches to make it easier to port the Android kernel features onto newer Linux kernels. I have heard from multiple sources that there are about 115 patches in the core part of the kernel (not related specifically to board support) for this.
If anyone knows where raw android kernel patches are available, please add a link here. See also the Android Kernel Features page for more information about individual kernel features.