It depends what they want to do. They can fork and take on the burden of maintaining the whole tree in which case good luck with that, linux is too much of a fire hose to enable a 3rd party to assemble something similar making different choices about what they merge. Otherwise they can maintain a re-based fork that tracks the Torvalds tree and then congratulations you’ve just invented a feature tree that can do contribution with extra steps.
I think car automation peaked at adaptive cruise control. It’s a simple tractable problem that’s generally well confined and improves the drivers ability to concentrate on other road risks.