Ask HN: How can I start contributing to RISC-V open processors

I am a digital designer engineer by profession who is working with verilog all the time. Having done some part time rails development in the past I have deep respect for the open source community and would like to make some contributions myself. I know open source contributions do not help the career at all in my current line of work and I don’t care about that. The recent momentum in RISC-V processors has made me think this is something I could contribute on and it would give me some chance to learn some advanced computer architecture stuff as well. Any suggestions on how I could begin would be welcome, in fact suggestions on open source contributions on something completely different would be appreciated as well.