Yes it does, in the HTML5 spec, under "Supported property names" of the document and form objects.
See http://www.w3.org/html/wg/drafts/html/master/dom.html#dom-document-namedItem-which for the form names on the document onkect
and http://www.w3.org/html/wg/drafts/html/master/infrastructure.html#htmlformcontrolscollection for the field names on the form controls collection.