Here we compile the BeagleBone Black Kernel, and generate an uImage file with the DTB blob appended to the kernel for ease of use.

git clone git://github.com/beagleboard/kernel.git
cd kernel
git checkout 3.8
./patch.sh
cp configs/beaglebone kernel/arch/arm/configs/beaglebone_defconfig
wget http://arago-project.org/git/projects/?p=am33x-cm3.git\;a=blob_plain\;f=bin/am335x-pm-firmware.bin\;hb=HEAD -O kernel/firmware/am335x-pm-firmware.bin
cd kernel
make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- beaglebone_defconfig -j4
make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- uImage dtbs -j4
make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- uImage-dtb.am335x-  boneblack -j4

Now we build any kernel modules:

make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- modules -j4

And if you have your rootfs ready, you can install them:

make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- INSTALL_MOD_PATH=.. modules_install