Policy for the preferred kernel tree

ff07

Hi, I’m doing the tasks for the summer bug fixing mentorship. I’d like to know which kernel tree is the preferred one to patch against. There are at least three possible options:

1. The LFD103 training uses Linus’ tree for demonstration.
2. linux-next: according to kernel documentation, "you may want to work from that tree rather than Linus Torvalds' mainline tree." [1]
3. Subsystem maintainer’s tree, from another kernel doc page, "most subsystem maintainers run their own trees and want to see patches prepared against those trees."[2]

I’d like to know which tree is the preferred one for the tasks? Is it required to prepare the patches as if it were to be sent to the subsystem maintainers, or follow the LFD103 would suffice? Or is it a part of the tasks and cannot be discussed? Thank you.

[1] https://www.kernel.org/doc/man-pages/linux-next.html
[2] https://www.kernel.org/doc/html/latest/process/submitting-patches.html#:~:text=Obtain a current source tree&text=Most subsystem maintainers run their,tree is not listed there.