docs: Expose alias tag in domain RNG schema

Though <alias> is ignored when defining a domain, it can cause
failure if one validates (e.g. virt-xml-validate) the XML dumped
from a running domain. This patch expose it in domain RNG schema
for all the devices which support it.

docs/schemas/domaincommon.rng

@@ -733,6 +733,9 @@
       <optional>
         <ref name="diskIoTune"/>
       </optional>
+      <optional>
+        <ref name="alias"/>
+      </optional>
       <optional>
         <ref name="address"/>
       </optional>
@@ -1098,6 +1101,9 @@
       <optional>
         <ref name="usbmaster"/>
       </optional>
+      <optional>
+        <ref name="alias"/>
+      </optional>
       <optional>
         <ref name="address"/>
       </optional>
@@ -1195,6 +1201,9 @@
   </define>
   <define name="filesystemtgt">
     <interleave>
+      <optional>
+        <ref name="alias"/>
+      </optional>
       <optional>
         <ref name="address"/>
       </optional>
@@ -1395,6 +1404,9 @@
           <empty/>
         </element>
       </optional>
+      <optional>
+        <ref name="alias"/>
+      </optional>
       <optional>
         <ref name="address"/>
       </optional>
@@ -1810,6 +1822,9 @@
           </optional>
         </element>
       </optional>
+      <optional>
+        <ref name="alias"/>
+      </optional>
       <optional>
         <ref name="address"/>
       </optional>
@@ -1893,6 +1908,9 @@
       <optional>
         <ref name="qemucdevTgtDef"/>
       </optional>
+      <optional>
+        <ref name="alias"/>
+      </optional>
       <optional>
         <ref name="address"/>
       </optional>
@@ -2011,6 +2029,9 @@
           <value>ich6</value>
         </choice>
       </attribute>
+      <optional>
+        <ref name="alias"/>
+      </optional>
       <optional>
         <ref name="address"/>
       </optional>
@@ -2036,6 +2057,9 @@
           </choice>
         </attribute>
       </optional>
+      <optional>
+        <ref name="alias"/>
+      </optional>
       <optional>
         <ref name="address"/>
       </optional>
@@ -2050,6 +2074,9 @@
           <value>none</value>
         </choice>
       </attribute>
+      <optional>
+        <ref name="alias"/>
+      </optional>
       <optional>
         <ref name="address"/>
       </optional>
@@ -2093,6 +2120,9 @@
           <ref name="guestfwdTarget"/>
           <ref name="virtioTarget"/>
         </choice>
+        <optional>
+          <ref name="alias"/>
+        </optional>
         <optional>
           <ref name="address"/>
         </optional>
@@ -2134,6 +2164,9 @@
           </interleave>
         </group>
       </choice>
+      <optional>
+        <ref name="alias"/>
+      </optional>
       <optional>
         <ref name="address"/>
       </optional>
@@ -2161,6 +2194,9 @@
           </choice>
         </attribute>
       </optional>
+      <optional>
+        <ref name="alias"/>
+      </optional>
       <optional>
         <ref name="address"/>
       </optional>
@@ -2173,6 +2209,9 @@
           <value>usb</value>
         </choice>
       </attribute>
+      <optional>
+        <ref name="alias"/>
+      </optional>
       <optional>
         <ref name="address"/>
       </optional>
@@ -2189,6 +2228,9 @@
         <ref name="qemucdevSrcTypeChoice"/>
       </attribute>
       <ref name="qemucdevSrcDef"/>
+      <optional>
+        <ref name="alias"/>
+      </optional>
       <optional>
         <ref name="address"/>
       </optional>
@@ -2237,6 +2279,9 @@
       <optional>
         <ref name="deviceBoot"/>
       </optional>
+      <optional>
+        <ref name="alias"/>
+      </optional>
       <optional>
         <ref name="address"/>
       </optional>
@@ -2356,12 +2401,6 @@
       </attribute>
     </optional>
   </define>
-  <!--
-      Devices attached to a domain.
-      Sub-elements such as <alias> are not documented here, as they
-      can only exist when generated for a live domain and are ignored
-      when defining a domain.
-    -->
   <define name="devices">
     <element name="devices">
       <interleave>
@@ -2970,4 +3009,17 @@
       <param name="pattern">(0x)?[0-9a-fA-F]{1,16}</param>
     </data>
   </define>
+  <define name='aliasName'>
+    <data type="string">
+      <param name="pattern">[a-zA-Z0-9_-]+</param>
+    </data>
+  </define>
+  <define name='alias'>
+    <element name='alias'>
+      <attribute name='name'>
+        <ref name='aliasName'/>
+      </attribute>
+    </element>
+    <empty/>
+  </define>
 </grammar>