add maxDepth on subresources doc

Author: Nightbr

core/operations.md

@@ -344,6 +344,49 @@ Note that the operation name, here `api_questions_answer_get_subresource`, is th
 It'll be automatically set to `$resources_$subresource(s)_get_subresource`. To find the correct operation name you
 may use `bin/console debug:router`.
 
+Add to that, you can control depth of subresources with the parameter `maxDepth`. For example, if `Answer` entity also have subresource such as `comments`, you would like to not generate the route `api/questions/{id}/answers/{id}/comments`. You can do this by adding the parameter maxDepth in ApiSubresource annotation or yml/xml file configuration.
+
+```php
+<?php
+// src/AppBundle/Entity/Question.php
+
+use ApiPlatform\Core\Annotation\ApiProperty;
+use ApiPlatform\Core\Annotation\ApiResource;
+use ApiPlatform\Core\Annotation\ApiSubresource;
+use Doctrine\ORM\Mapping as ORM;
+
+/**
+ * @ORM\Entity
+ * @ApiResource
+ */
+class Question
+{
+    /**
+     * @ORM\Column(type="integer")
+     * @ORM\Id
+     * @ORM\GeneratedValue(strategy="AUTO")
+     */
+    private $id;
+
+    /**
+     * @ORM\Column
+     */
+    public $content;
+
+    /**
+     * @ORM\OneToOne(targetEntity="Answer", inversedBy="question")
+     * @ORM\JoinColumn(referencedColumnName="id", unique=true)
+     * @ApiSubresource(maxDepth=1)
+     */
+    public $answer;
+
+    public function getId()
+    {
+        return $this->id;
+    }
+}
+```
+
 ## Creating Custom Operations and Controllers
 
 API Platform can leverage the Symfony routing system to register custom operation related to custom controllers. Such custom