conf: support <dtb> tag in XML domain file

docs/formatdomain.html.in

@@ -232,6 +232,7 @@
     <kernel>/root/f8-i386-vmlinuz</kernel>
     <initrd>/root/f8-i386-initrd</initrd>
     <cmdline>console=ttyS0 ks=http://example.com/f8-i386/os/</cmdline>
+    <dtb>/root/ppc.dtb</dtb>
   </os>
   ...</pre>
 
@@ -253,6 +254,10 @@
         the kernel (or installer) at boottime. This is often used to
         specify an alternate primary console (eg serial port), or the
         installation media source / kickstart file</dd>
+      <dt><code>dtb</code></dt>
+      <dd>The contents of this element specify the fully-qualified path
+        to the (optional) device tree binary (dtb) image in the host OS.
+        <span class="since">Since 1.0.4</span></dd>
     </dl>
 
     <h4><a name="eleemntsOSContainer">Container boot</a></h4>

docs/schemas/domaincommon.rng

@@ -367,6 +367,7 @@
             <value>g3beige</value>
             <value>mac99</value>
             <value>prep</value>
+            <value>ppce500v2</value>
           </choice>
         </attribute>
       </optional>
@@ -835,6 +836,11 @@
           <text/>
         </element>
       </optional>
+      <optional>
+        <element name="dtb">
+          <ref name="absFilePath"/>
+        </element>
+      </optional>
     </interleave>
   </define>
   <define name="osbootdev">