section 152(6)

A company in which public substantially interested "Retire by Rotation" provision shall apply. In this case all the Directors (2/3) who are appointed on rotatinal basis, out of them 1/3 directors shall retire at every AGM and Director who are for long time on the office of Director shall retire first.

So you can retire by AGM is covered by retire by Rotation.

Retire by AGM is also applicable in case of Additional Director (AD) because after the appointment of AD, he shall hold office till the AGM therefore it is necessary to regularise that director in AGM otherwise he will retire automatically and this provision shall apply to all the Companies who appoints Additional Director.