The kernel maintainers are Neil Armstrong, Kevin Hilman and (reviewer) Martin Blumenstingl. Their contacts are publicly available in kernel sources. I’m someone with an unhealthy passing interest in Amlogic upstream support and matters related to Kodi, but I am not a kernel maintainer. Furkhan is similarly not a kernel maintainer but he likes to see Manjaro run on everything
NB: Sending board samples to maintainers supports the process of validating and accepting the code submissions you make to add support for your boards to the upstream kernel. It doesn’t meant they write free code to add support for your boards. Community developers are more likely to do that for you, but as SOM boards need a lot more skill and effort to test than self-contained boards like BPI-M5 this is (IMHO) best done by the manufacturer.