Add section on China registry mirror (#3379)

docs/recipes/mirror.md

@@ -100,3 +100,22 @@ to make the change persistent.
 ```
 
 Save the file and restart Docker for the change to take effect.
+
+## Use case: the China registry mirror
+
+The URL of the registry mirror for China is `registry.docker-cn.com`. You can pull 
+images from this mirror just like you do for other registries by specifying
+the full path, including the registry, in your `docker pull` command, for example:
+
+```bash
+$ docker pull registry.docker-cn.com/library/ubuntu
+```
+
+Or you can add "https://registry.docker-cn.com" to the `registry-mirrors` array
+in `/etc/docker/daemon.json` to pull from the China registry mirror by default.  
+
+```json
+{
+  "registry-mirrors": ["https://registry.docker-cn.com"]
+}
+```