Naturalised Parent Travelling to Ireland with Non-Irish infant (Not on FBR yet)

Hey guys, what sort of visa/permission an infant who is born in a Non-EEA country (that requires visa for Ireland), needs when travelling to Ireland for first time, with their Irish (Naturalised) parent?

Thanks

wouldn't it be join family visa, as they're joining an Irish citizen for now? although it'll take a while in terms of processing time

Join family is an obvious thing but i heard that infants don't need visa and can travel with mother as long as they have birth certificate. Someone might be able to shed light on this. I myself came across a family who were at immigration counter and explained the situation, and were allowed to board after showing a document from Immigration website. I can't find any such thing though.

or can an infant travel on visit visa with an aim of changing it later?