man: SYMLINK can be matched as well as assigned

If by-path / by-id links don't quite do what you want, this is a nice
clean way to extend the behaviour.  Real example:

SYMLINK=="serial/by-id/usb-Novatel_Wireless_Inc*CDMA*-if00-port0", \\
 SYMLINK+="cellcard"

Some users ask how to do things like this.

 - create an additional link with a shorter name
 - create a link which matches more loosely
    (omit certain path segments e.g. serial numbers)
 - change permissions on certain USB device nodes

Allow them to realize this without reading the friendly *.c files.

Signed-off-by: Alan Jenkins <alan-jenkins@tuffmail.co.uk>

udev/udev.xml

@@ -166,6 +166,16 @@
               </listitem>
             </varlistentry>
 
+            <varlistentry>
+              <term><option>SYMLINK</option></term>
+              <listitem>
+                <para>Match the name of a symlink targeting the node. It can
+                be used once a SYMLINK key has been set in one of the preceding
+                rules. There may be multiple symlinks; only one needs to match.
+                </para>
+              </listitem>
+            </varlistentry>
+
             <varlistentry>
               <term><option>SUBSYSTEM</option></term>
               <listitem>
@@ -295,7 +305,7 @@
             <varlistentry>
               <term><option>SYMLINK</option></term>
               <listitem>
-                <para>The name of a symlink targeting the node. Every matching rule can add
+                <para>The name of a symlink targeting the node. Every matching rule will add
                 this value to the list of symlinks to be created along with the device  node.
                 Multiple symlinks may be specified by separating the names by the space
                 character.</para>