[PATCH] Documentation: how to apply patches for various trees

Add a new document describing the major kernel trees and how to apply their
patches.

Signed-off-by: Jesper Juhl <jesper.juhl@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>