Car companies often don't do the embedded development themselves. They usually rely on suppliers and a vast network of contractors to do most of that work, thou

Car companies often don't do the embedded development themselves. They usually rely on suppliers and a vast network of contractors to do most of that work, though things have been shifting back in-house in recent years for velocity/feature/security/bug fixing/institutional knowledge reasons. Some of that is becoming more open source, e.g. I've seen work from Ford and GM being open sourced, but it's relatively uncommon compared to the higher level stack.