[1] https://lore.kernel.org/lkml/CAHk-=wjbtip559HcMG9VQLGPmkurh5...
[1] https://lore.kernel.org/lkml/CAHk-=wjbtip559HcMG9VQLGPmkurh5...
https://github.com/torvalds/linux/pull/17#issuecomment-56546...
Without involving github at all, you can use git directly to push branches to a remote repository and then have it be merged by the maintainers there, which leads to a workflow that's pretty similar to the one you have with github.
Instead, Linux is being worked on by exporting the (git) patches and sharing them on a mailing list, effectively not using a significant feature of git and leading to a very different workflow than the one everyone else is using (github users and others alike), so I still find the question legitimate.
Once configured, you can send a series of patches to the mailing list with a single git command, and with just another command apply a series of patches from the mailing list. It's actually quite efficient.