This should be `graphdriver/zfs: ...`, shouldn't it?  (since this specifies the exact path)

It seems a little strange to me to add a MAINTAINERS entry for a path that doesn't exist yet. :)

If the path did exist, it'd be easy for you to add a `graphdriver/zfs/MAINTAINERS` file, which would be a better way to handle this - so you probably just want to add that to your fork, and we can look to merge just the contrib change for now until you're ready to submit a PR. :) /cc @shykes