DMV points differ by state. Some states do not have any type of point systems while many do and assess points for most moving violations. A conviction for seat belt ticket will be assigned points in some states and is not in other states. So since state laws and points schedules vary you will need to contact your state's Department of Motor Vehicles to find out if a conviction on a seat belt violation will cause points to be placed on your driving record.
It might even depend upon on the type of seat belt offense you were cited for violating by law enforcement. For example in New York State if a driver is convicted of a violation where a passenger under age 16 is not wearing a seat belt or in a child safety seat, 3 points are assigned to the driver's record. If convicted of a seat belt violation involving the driver or a passenger age 16 or older, no points are assigned to the driver's record.
Florida is another state in which there is not a listing for points for a driver being cited for a seat belt violation however if the ticket was for a child restraint violation ticket then 3 points are assigned.