Add info about vendor prefixing templates

development/extensions/tutorial_controllers.rst

@@ -95,7 +95,7 @@ Every controller should contain at least two methods:
             $l_message = !$this->config['acme_demo_goodbye'] ? 'DEMO_HELLO' : 'DEMO_GOODBYE';
             $this->template->assign_var('DEMO_MESSAGE', $this->language->lang($l_message, $name));
 
-            return $this->helper->render('demo_body.html', $name);
+            return $this->helper->render('@acme_demo/demo_body.html', $name);
         }
     }
 
@@ -154,6 +154,31 @@ title, and the status code as its arguments. The page title defaults to an
 empty string and the status code defaults to 200. We are using the
 `Controller template`_ ``demo_body.html``.
 
+.. tip::
+
+    When calling a template file from PHP using ``phpbb\controller\helper:render()``
+    template files are searched for in two places (and in this order):
+
+        1. phpBB/styles/*style_name*/template/
+        2. phpBB/ext/*all_active_extensions*/styles/*style_name*/template/
+
+    The following code will load a template that could be located in any of the
+    above locations, i.e., in any phpBB style or active extension:
+
+    .. code-block:: php
+
+        $this->helper->render('demo_body.html', $name);
+
+    If you only need to load a template file from within your own extension,
+    we recommend using the ``@vendor_extension/`` prefix:
+
+    .. code-block:: php
+
+        $this->helper->render('@acme_demo/demo_body.html', $name);
+
+    It is also recommended to always use unique names for your templates to avoid possible
+    conflicts with phpBB's templates or other extensions.
+
 .. note::
 
     The ``phpbb\controller\helper:render()`` method returns a Symfony