Where is the core.sys (and std.windows) documentation?

[SomeGuy via Digitalmars-d-learn]

I can't find the core.sys documentation in the library reference. 
I thought that functionality was removed but clearly the source 
files exist in druntime: 
https://github.com/dlang/druntime/tree/master/src/core/sys

Same goes for std.windows: 
https://github.com/dlang/phobos/blob/master/std/windows/registry.d.