For the L4T 32.5.1 release, there is a minor error in the Developer Guide.
In Kernel customization subsection Manually Downloading and Expanding Kernel Sources, 4. Extract the kernel source file.
The hyphen in
$ tar –xjf kernel_src.tbz2 is not a valid English character.
In addition, when following Obtaining the Kernel Sources with Git, obtained folder name is sources, but when following Manually Downloading and Expanding Kernel Sources, the obtained folder name is source. I’m not sure if this is intended. In the L4T release package, the original folder name is source, which contains nv_src_build.sh.