I have a simple 10.2.2 file geodatabase (tried 10.3.0, same results) with one polygon feature class, metadata, some domains, and subtypes based on one of the fields with a domain. I generated it brand new by copy/pasting the feature class from a 10.2.2 enterprise geodatabase in SQL Server, so it's not likely to be corrupt. ArcGIS Online and Open Data variously ignore the domains and subtypes when I try to either upload the zipped fGDB as a "File Geodatabase" item or publish from ArcMap as a "Feature Layer (Hosted)" item. The ArcGIS for Desktop and ArcGIS Online Help have not yielded any guidance that would get my fGDB into AGO successfully.
So... have any of you come up with workarounds, incantations, or any undocumented secrets for success?