GitHub is smart enough to update a pull request with any more commits you make on the branch you're trying to merge in.  So if anyone commits to lalezaris:master, those commits will show up here automatically and are part of the pull request.  There's no need to close/resubmit the PR as long as you stay on the same branch.  Once more work has been done, you can comment and ask for more review, and repeat until a few committers have okayed the PR.