This reminded me of https://mveg.es/posts/writing-a-device-driver-for-unix-v6/, which was recently discussed here under https://news.ycombinator.com/item?id=30679923

Also... have you considered contributing this content to the NetBSD Internals book? https://www.netbsd.org/docs/internals/en/netbsd-internals.ht... :)