Hi,
I didn’t compiled kernels for long time but you can go and download it form kernel.org, patch it renemae it and compile it.
Unfortunately the dev tools are broken for last releases, last that you can use is
3.7.1
I compiled some instructions some time ago, there is also an old post in italian how to do it.
Other option is to do a cross compile on ubuntu. Never did this but should be another way.
I just ordered a new apu2 unit ( 4 core, 4g ) so I might look into myself sometime in jan when arrive and if I have time.