How to diff to patch with relative paths

[Michael]

Hello,

Background, we're maintaining a core Arch (ARM) Linux kernel through a
Git repository to submodule approach, the submodule being the core
kernel code.

I want to diff the code we've been maintaining as a patch on the core
kernel. I am familiar with the basic approach, diff to get the patch
file, patch the file into an extracted kernel code base, and so on.

What I need to know is, what option(s) to use so that when we get the
diff, regardless of the paths involved, I want to patch with a
relative path, not absolute. Especially because developer paths can be
different maintaining the platform-specific mods.

Thank you...

Regards,

Michael Powell