Once installed, the kernel source code is included in the SDK's board-support directory.
This is done using the Linux kernel configuration system.
NOTEAny time you make a change to the kernel which requires you to recompile it you should also insure that you recompile the kernel modules and reinstall them.
Otherwise all your kernel modules may refuse to load which will result in a significant loss of functionality.
When you want to customize the kernel configuration the easiest way is to use the built in kernel configuration systems.
Two of the most popular configuration systems are: menuconfig: an ncurses based configuration utility NOTE: on some systems in order to use xconfig you may need to install the libqt3-mt-dev package.
This wiki will cover the basic steps for building the Linux kernel.