You could look a the commit logs and see if there’s any email domains that pique your interest.
Depends a bit on your ideas of "reputable"; IIRC, hardware OEMs tend to employ devs to implement hardware support for their boards, but a rather lot of those have a poor reputation in terms of code quality - i.e., "We've successfully shipped the device with kernel 5.1.0 (current when we started); time to forget about that and implement the next board! What do you mean, upstreaming? That sounds like extra work. Bug fixes? Don't be absurd!".