HTML-AAM: should we have some general language for sub-doms?

[cyns]

Canvas has an author-supplied sub-dom, which also maps into the accessibility api tree
The audio and video elements can have a whole tree of children if @controls is present.
Should we add some general language to the document on how to handle these situations?

Here's what we have for UIA for canvas now. It seems inadequate.
Control Type: Image
NOTE: subdom elements will be mapped separately.

[jasonkiss]

This issue was moved to w3c/html-aam#3