Allow Portal for ArcGIS to restrict the scope of a Geocode search by passing parameters in the same way as is allowed in ArcGIS online. So for example to restrict the Geocode service in AGOL you can append sourceCountry=AUS which works well.
http://geocode.arcgis.com/arcgis/rest/services/World/GeocodeServer?sourceCountry=AUS
Unfortunately the same does not work in Portal and it will not accept the Geocode Service when parameters are appended to the URL.