Added class-level docblock to new interface

src/ValidatorProviderInterface.php

@@ -1,13 +1,23 @@
 <?php
-
 /**
  * @link      http://github.com/zendframework/zend-validator for the canonical source repository
- *
  * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
  * @license   http://framework.zend.com/license/new-bsd New BSD License
  */
+
 namespace Zend\Validator;
 
+/**
+ * Hint to the zend-modulemanager ServiceListener that a module provides validators.
+ *
+ * Module classes implementing this interface hint to
+ * Zend\ModuleManager\ServiceListener that they provide validators for the
+ * ValidatorPluginManager.
+ *
+ * For users of zend-mvc/zend-modulemanager v2, this poses no backwards-compatibility
+ * break as the method getValidatorConfig is still duck-typed within Zend\Validator\Module
+ * when providing configuration to the ServiceListener.
+ */
 interface ValidatorProviderInterface
 {
     /**