I have written a post on how to add and integrate custom lint rules to your android app, you can have a look. It also has links to github repos showing how its done in an android project.
Link to post
The easiest way for me was to set ANDROID_LINT_JARS path in the gradlew file and point it to the custom lint jar which is checked in to VCS system, so that you can run it locally as well before pushing the code.
Hope it helps.