The official docs come with the particular release you are using and are for cross compiling on a host PC. See to particular release you are using (L4T release found with “head -n 1 /etc/nv_tegra_release”):
More of a tutorial on kernel build configuration:
https://forums.developer.nvidia.com/t/topic/229155/12
More of a tutorial on building a kernel:
https://forums.developer.nvidia.com/t/topic/193640/11