Individuals making significant and valuable contributions are given commit-access to the project. These individuals are identified by the TC and discussed during the weekly TC meeting.
If you make a significant contribution and are not considered for commit-access log an issue and it will be brought up in the next TC meeting.
Internal pull-requests to solicit feedback are required for any other non-trivial contribution but left to the discretion of the contributor.
For significant changes wait a full 48 hours (72 hours if it spans a weekend) before merging so that active contributors who are distributed throughout the world have a chance to weigh in.
Controversial changes and very significant changes should not be merged until they have been discussed by the TC which will make any final decisions.
TC members nominate contributors to be added to the TC which the TC will vote on. They can nominate any individual during any meeting.