Reviving this thread to give some clarity. I'm wiring something similar. I plan to have my parking lights give a one-time flash when the doors are locked with my fob.
For your application though, I've got an idea of what needs to be done:
First off, I recommend using fused relays, or at least placing a fuse in the new circuit you're creating.
You would need a [either 4 or 5 pin] relay that turns the PL (parking lights) on with the dome light.
To keep these 2 circuits separate when the ignition is ON or started, you need to install a 5 pin relay (this one NEEDS to be a 5 pin relay) to one of the "SWITCHED hot" wires (usually pink colored) under your dash. The "switched hot" wire will act as the exciter for the relay, that shuts the circuit OFF when ignition is switched ON.
Basically, when the "switched on" wire gives voltage to the 5 pin relay as the exciter, the relay switches the completed circuit from the PL hot wire to a dead connection.
That way, whenever the ignition is ON or started, the dome light and parking lamps have nothing to do with each other, and will operate separately until the vehicle is shut off.
I would recommend placing a rocker switch in the dome/PL circuit that will separate the two on command, in case you want to use your dome light when the vehicle is off, without having your PL come on.
I won't give exact wire-to-pin directions for these relays, but if you know how relays work, you'll be fine. If there's demand for me to explain further, then I will.
Otherwise, have a great night!
-Jacob