Anyone can submit a patch for consideration by the committers.
To do so, create a Bugzilla issue or use an appropriate existing issue, and add the patch as an attachment.
The patch should be in the form of a a file in diff -u format, as generated by the svn diff or git diff commands from the current trunk sources.
Before submitting a patch, or any code for use by the project, you should have a Contributor's License Agreement (CLA) on file with the ASF.
Here are the instructions for filing a CLA.
Instructions for PMC regarding CLAs for people who submit code:
When someone creates an attachment on our Bugzilla, if their login email address is already flagged as having a CLA, there will be a green checkmark shown after the submitter name on the attachment line.
If it isn't there, check if ASF has a CLA on file for that email address (ASF committer login required).
If a CLA is not on file, direct them to this page for instructions on submitting a CLA.
Once they have a CLA on file, someone with administrator privileges on Bugzilla should click on Administration, then Users, than search for the email address, edit the user, then select the checkbox for hascla.