How to track the source tree of kernel

[chen.mingzheng]

Hi Guys,

Sorry to bother you all. I'm just starting learning linux with a rpi4b. 
I found the raspi source tree have many branches, which are different 
from the kernel source tree, which also have many branches. I want to 
know how should I track the source code. should I track all branches 
from the remote repo, or just stick to a specific branch? How did you do 
so that you can catch up to lastest kernel?

Thanks in advance!

Sincerely,
A Linux newbies.