Adding tools to the collection

So - the other day I asked about Web Annotation testing via WPT and the
consensus seemed to be that was fine.  The advice was also to add any
"tooling" to wpt-tools.  That makes sense to me.  My question is "Is there
a process for doing PRs that include a repository and a sub-repository?"
 And on a related note, is there a document somewhere that talks about how
to have a fork of wpt-tools integrated as a sub-module of a fork of WPT
itself?  'cause that feels above my pay grade!

-- 
Shane McCarron
Projects Manager, Spec-Ops