If my son was born in US but going to China to stay with grandmother what kind of visa does he need?

My son was born in the US but is traveling back to China to stay with his grandmother and other family. What kind of visa can he get to allow him constant travel back and forth between countries to stay with his 2 families in China and US? He is a year old right now and he will travel often for the next few years. I had heard the was a visa that allowed family to travel back to China repeatedly and indefinitely if their relatives were still living there. Is that true?