What is the process to get dot1q sub interface support into the roadmap?

I'm not sure what all the work would entail for an addition like this, but my org has use cases where having that support would make for a more usable SONiC experience.

Here is a currently open issue with someone else who has encountered the issue that I've also encountered:
sonic-net/SONiC#109

They say that it has been resolved, but in my latest testing that is not the case.

Anyway, please advise on the proper process!

thanks,
stegen