aether-2.0.0 models: Reorganize the YANG tree as submodules

Change-Id: I5c41899b466f7ece528d5e078924589118441104
diff --git a/config-models/aether-2.0.x/files/yang/onf-ip-domain.yang b/config-models/aether-2.0.x/files/yang/onf-ip-domain.yang
index e896cc5..b5fb974 100755
--- a/config-models/aether-2.0.x/files/yang/onf-ip-domain.yang
+++ b/config-models/aether-2.0.x/files/yang/onf-ip-domain.yang
@@ -2,14 +2,12 @@
 //
 // SPDX-License-Identifier: LicenseRef-ONF-Member-Only-1.0
 
-module onf-ip-domain {
-  namespace "http://opennetworking.org/aether/ip-domain";
-  prefix ipd;
+submodule onf-ip-domain {
+  belongs-to onf-enterprise { prefix ent; }
 
   import ietf-inet-types { prefix inet; }
   import ietf-yang-types{ prefix yg; }
   import onf-aether-types { prefix at; }
-  import onf-enterprise{ prefix ent; }
 
   organization "Open Networking Foundation.";
   contact "Scott Baker";
@@ -18,6 +16,11 @@
      that may be assigned to UEs, as well as DNS servers and other
      metadata";
 
+  revision "2022-01-14" {
+    description "Refactored as submodule";
+    reference "RFC 6020";
+  }
+
   revision "2021-06-02" {
     description "An Aether IP and Domain Specification";
     reference "RFC 6087";
@@ -30,15 +33,15 @@
     description "The typedef for ip-domain-id";
   }
 
-  container ip-domain {
-    description "The top level container";
+  grouping ip-domain {
+    description "The ip-domain grouping";
 
     list ip-domain {
-      key "id";
+      key "ip-id";
       description
         "List of ip domains";
 
-      leaf id {
+      leaf ip-id {
         type ip-domain-id;
         description "ID for this ip domain.";
       }
@@ -88,17 +91,6 @@
         type at:description;
         description "description of this ip domain";
       }
-
-      // Ip-Domain is always owned by an Enterprise, because it contains
-      // IP addresses relative to that Enterprise.
-      leaf enterprise {
-        type leafref {
-          path "/ent:enterprise/ent:enterprise/ent:id";
-        }
-        mandatory true;
-        description
-          "Link to enterprise that owns this IP-Domain";
-      }
     }
   }
 }