Hi Qingping. I'll largely leave this to Nick, but here's a ticket concerning this exact topic...
https://trac.torproject.org/projects/tor/ticket/8891
Personally I'm a little interested in it since this would make it worthwhile for me to add a hidden service descriptor parser to stem.
I suspect this will need a proposal. As for a spec patch, that would certainly be welcome once this has been added to tor (we want to update them together).
Cheers! -Damian