I'm honestly not sure at the moment. Some port committers don't mind, at least not for new ports, some do mind. And there's also a transition from subversion to git going on right now. I maintain a port but it's an existing port, so I just upload a diff with the changes. That gets applied and approved by a committer and then it's pushed to the ports tree.
I'd try submitting a tar archive but be prepared that you may have to replace it with a diff or patch file when a committer asks for it. As long as you make it as easy as possible for them things usually work out quite quickly. When you submitted your PR wait some time, if nobody looked at it for, say, 2 weeks, then send a ping to the freebsd-ports@ mailing list. It's also worthwhile to sign up for that mailing list in any case. If you have specific questions on how to implement certain port related things you can ask there too.