If someone is still searching for a solution:
First go to RPCS3 Settings using F1 and install the PSN Game.
Then Create a link file: roms\PS3\Game.psn (Game is jour Game Title, just be sure it ends with .psn)
Content of Game.psn is the “Serial” of the Game shown in RPCS3
Take a look at the Wiki
https://wiki.batocera.org/systems:ps3
--> RUN PSN Games
