Add region field to device form

netbox/dcim/forms.py

@@ -1670,8 +1670,15 @@ class PlatformCSVForm(CSVModelForm):
 #
 
 class DeviceForm(BootstrapMixin, TenancyForm, CustomFieldModelForm):
+    region = DynamicModelChoiceField(
+        queryset=Region.objects.all(),
+        required=False
+    )
     site = DynamicModelChoiceField(
-        queryset=Site.objects.all()
+        queryset=Site.objects.all(),
+        query_params={
+            'region_id': '$region'
+        }
     )
     rack = DynamicModelChoiceField(
         queryset=Rack.objects.all(),

netbox/templates/dcim/device_edit.html

@@ -21,6 +21,7 @@
     <div class="panel panel-default">
         <div class="panel-heading"><strong>Location</strong></div>
         <div class="panel-body">
+            {% render_field form.region %}
             {% render_field form.site %}
             {% render_field form.rack %}
             {% if obj.device_type.is_child_device and obj.parent_bay %}