I'm not sure that I understand the purpose of this section, considering that nothing is declared "special" about these 
file system names. What I mean is that the spec says HOME (for example) is well known, but then does not either reserve 
this file system name, or pre-define it. If these names are going to be called out as well known, perhaps they should be
 pre-defined with a default, with allowable changes to certain sub-elements (e.g. mount point/mount source).

Also ... I don't think we can say that ROOT is well known, as a Windows system has multiple ROOT filesystems (one for 
each mounted volume, in fact).