[MNG-4840] document requiredMavenVersion in plugin descriptor

maven-plugin-api/src/main/java/org/apache/maven/plugin/descriptor/PluginDescriptor.java

@@ -77,6 +77,7 @@ public class PluginDescriptor extends ComponentSetDescriptor implements Cloneabl
 
     private String description;
 
+    // MNG-4840
     private String requiredMavenVersion;
 
     private Plugin plugin;
@@ -295,10 +296,22 @@ public class PluginDescriptor extends ComponentSetDescriptor implements Cloneabl
         return description;
     }
 
+    /**
+     * Set required Maven version.
+     *
+     * @param requiredMavenVersion Maven version required by the plugin
+     * @since 3.0.2
+     */
     public void setRequiredMavenVersion(String requiredMavenVersion) {
         this.requiredMavenVersion = requiredMavenVersion;
     }
 
+    /**
+     * Get required Maven version.
+     *
+     * @return the Maven version required by the plugin
+     * @since 3.0.2
+     */
     public String getRequiredMavenVersion() {
         return requiredMavenVersion;
     }

maven-plugin-api/src/main/mdo/plugin.mdo

@@ -92,6 +92,15 @@ under the License.
           <type>boolean</type>
           <defaultValue>true</defaultValue>
         </field>
+        <field>
+          <name>requiredMavenVersion</name>
+          <version>1.0.0</version>
+          <description>
+            Minimum Maven version required to use the plugin.
+            @since Maven 3.0.2
+          </description>
+          <type>String</type>
+        </field>
         <field xdoc.separator="blank">
           <name>mojos</name>
           <version>1.0.0</version>