Seeed nvidia AGX Orin H01 custom kernel

I’ve purchased Seeed NVIDIA AGX Orin H01 for a project involving new video related hardware. When trying to build a customized Linux kernel for the board, I noticed that the Linux kernel image is provided by Seeed as a binary in the AGX-Orin-32GB-H01-JP5.1.1.zip which can be found from the Wiki:

In order to do the necessary modifications, I would like to get the corresponding Linux kernel source code and build scripts. Can you please point me to the location where these can be obtained.