If you are sufficiently motivated, NT 4 leaked many years ago and you could find it; it even has interesting things like DEC Alpha support & various subsystems still included IIRC. Perhaps you could find a newer version like 5.2 on GitHub or another site, but beware, as a Linux dev/contributor, you probably don't want to have access to that.
FWIW, I've stumbled upon both of those things in my personal research while I had legitimate access to the 5.2 sources as a student. It turns out Bing will link you directly to the Windows source code if you search for <arcane MASM directive here>.
Yes, I'm in the process of reporting this to Microsoft and cleansing myself of that poison apple.
It is not true that internal architecture of Linux drivers is not clearly defined. It is just a practical approach to maintenance of drivers (as an author of one Linux hardware driver I'm pretty sure the best possible). Reasoning is outlined in famous "Stable API nonsense" document http://elixir.free-electrons.com/linux/latest/source/Documen...
I don't think Windows approach is worth praising here. It results in a lot of drivers stopping working after few major Windows release upgrades. In Linux, available drivers can be maintained forever.