Is Jordanstown station parking intended for rail passengers?

Yes.

Jordanstown train station is listed as a rail Park and Ride. It serves people who want to join the train instead of taking the car along the Belfast Lough corridor. Greenisland and Whiteabbey have separate rail parking entries, so search for the precise station you intend to use; they are not alternate names for one car park. Check which local trains serve Jordanstown and take account of the time needed to walk between the car park and platform.