Found a blog post that gives a quick overview of how to do git via email in general: https://peter.eisentraut.org/blog/2023/05/09/how-to-submit-a-patch-by-email-2023-edition
So at least from my understanding you’d make your changes, email the contents of the patch to the maintainer, and then they’d apply it on their side, do code review, email you comments, etc. until it was in an acceptable state.
There’s also the full kernel development wiki that goes into all the specifics: https://www.kernel.org/doc/html/v4.16/process/howto.html
(I never got through the whole thing)
Another solution to this situation is to squash your changes in place so that your branch is just 1 commit, and then do the rebase against your master branch or equivalent.
Works great if you’re willing to lose the commit history on your branch, which obviously isn’t always the case.