This is how PEs should be certified. Sadly, licensure of PEs varies by state.

In Florida, the title of "software engineer" requires a license. To obtain the license, you only need to pass the national engineering (I forgot the exact name of the organization) exam for software engineering. The national exam was withdrawn some years ago. I wrote the Florida Engineering Board about it, suggesting that they needed to update the requirements.

Their response? Florida doesn't distinguish between PE specialties; prospective software engineers should just get a PE license in another field. They suggested electrical engineering.

So in Florida, the PE signing off on your buildings's wiring might be a chemist, or the PE supervising a bridge construction might be only trained in electrical engineering.