To submit pull requests for mx, you need to sign the Oracle Contributor Agreement. There is a white-list for contributors who have signed the OCA so please add a comment to your first pull request indicating the name you used to sign the OCA if it isn't clear from your github profile.
Pull requests can only be merged by committers and a committer cannot merge his or her own pull requests.
When creating a pull request, make sure you designate an assignee to ensure the request is processed in a timely manner.