Bargman and Hopkins have published a "standard", but in reality it is more of a "gentleman's agreement". You can wire your trailer anyway you want to. There is no official agency that will write you a ticket for violating the "standard".
It pays to follow the Bargman/Hopkins diagrams, so everything is the same, but it is not required by law or regulation.
https://www.google.com/search?q=bargman+rv+trailer+wiring+diagram&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwifoNTpwpbUAhUIsVQKHfbbDAgQsAQIIw&biw=1536&bih=731