Module Name Resolution

[Jason C. Wells via Digitalmars-d-learn]

I am reading through: https://dlang.org/spec/module.html. I'll 
soon be working through a previous example provided by Mike 
Parker.

I am reading through Ketmar's iv.d/nanovg/package.d:

   module iv.nanovg;
   public import iv.nanovg.nanovg;

This looks like three levels of hierarchy, but is it?

Should I interpret that import as:

iv
  --nanovg
     --nanovg

Perhaps it really means:

iv.nanovg
   --nanovg

I'm a little confused because the corresponding directory in 
ketmar's source code is named "iv.d" rather than "iv" which is 
what I would have thought to find based on the import.

I see mention of a subpackage in my previous thread. Is this how 
a subpackage is implemented?

Thanks,
Jason