The Apple Car's autonomous driving subsystem processing power has reportedly been tasked to the Apple Silicon department responsible for the A15 or M1 chipsets. Apple is apparently developing the self-driving chip for its car project in partnership with Korean OSAT (outsourced semiconductor package test) companies just as it did for the M1 processor.
https://www.notebookcheck.net/Apple-Car-s-self-driving-processor-modules-to-be-packaged-by-Korean-companies-just-like-Tesla-s-FSD-chip.602273.0.html