docs/zh_CN: add devicetree index translation

Translate .../devicetree/index.rst into Chinese.
Signed-off-by: Yanteng Si <siyanteng@loongson.cn>
Reviewed-by: Alex Shi <alexs@kernel.org>
Link: https://lore.kernel.org/r/0a01f2eee980da02c0810d3d99b95af9013b646f.1646642188.git.siyanteng@loongson.cnSigned-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/translations/zh_CN/devicetree/index.rst

+.. SPDX-License-Identifier: GPL-2.0
+.. include:: ../disclaimer-zh_CN.rst
+
+:Original: Documentation/Devicetree/index.rst
+
+:翻译:
+
+ 司延腾 Yanteng Si <siyanteng@loongson.cn>
+
+:校译:
+
+
+=============================
+Open Firmware 和 Devicetree
+=============================
+
+该文档是整个设备树文档的总目录，标题中多是业内默认的术语，初见就翻译成中文，
+晦涩难懂，因此尽量保留，后面翻译其子文档时，可能会根据语境，灵活地翻译为中文。
+
+内核Devicetree的使用
+=======================
+.. toctree::
+   :maxdepth: 1
+
+Todolist:
+
+*   usage-model
+*   of_unittest
+*   kernel-api
+
+Devicetree Overlays
+===================
+.. toctree::
+   :maxdepth: 1
+
+Todolist:
+
+*   changesets
+*   dynamic-resolution-notes
+*   overlay-notes
+
+Devicetree Bindings
+===================
+.. toctree::
+   :maxdepth: 1
+
+Todolist:
+
+*   bindings/index

Documentation/translations/zh_CN/index.rst

@@ -56,10 +56,14 @@ TODOList:
 
 下列文档描述了内核需要的平台固件相关信息。
 
+.. toctree::
+   :maxdepth: 2
+
+   devicetree/index
+
 TODOList:
 
 * firmware-guide/index
-* devicetree/index
 
 应用程序开发人员文档
 --------------------