So those come from armbian and mainline kernel, as I expected.
Well, I wouldn't say that. If patches would be present in mainline already, there wouldn't be need to have them. I also don't see such patch in Armbian, so I suspect it's original work from PR author. Anyway, soon PR will need a rebase becasue patches pulled from linux-next will break it.
As far as I understand I could fetch the commits from that pull request,
You could also pull directly from PR author's github. That way you don't need to pick commits.
do I need to also make an specific "target" for the Orange Pi Lite 2? Where are the target files for the supported devices located in the git repo?
There is no specific board handling done in build system, except in scripts/uboot_helper, but that's already handled in PR. Even SoC specific handling will slowly get away, at least from patch perspective. Wifi chip is already supported in mainline and package which provides broadcom wifi firmwares already supports it.