Our docs mention frequently that Gerrit code review is for MediaWiki core and extensions, but nowadays is more than that, isn't it? It would be better to say that we use Gerrit code review for anything. If there are exceptions (projects using GitHub only) then we can specify them somewhere.
Also, since we have everything mirrored in GitHub it would be nice to tell (especially to newcomers) what to do with that, and whether patches can be submitted that way.