devlink: add documentation for hns3 driver

Add a file to document devlink support for hns3 driver, now support devlink
info and devlink reload.

Signed-off-by: Hao Chen <chenhao288@hisilicon.com>
Signed-off-by: Guangbin Huang <huangguangbin2@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/networking/devlink/hns3.rst

+.. SPDX-License-Identifier: GPL-2.0
+
+====================
+hns3 devlink support
+====================
+
+This document describes the devlink features implemented by the ``hns3``
+device driver.
+
+The ``hns3`` driver supports reloading via ``DEVLINK_CMD_RELOAD``.
+
+Info versions
+=============
+
+The ``hns3`` driver reports the following versions
+
+.. list-table:: devlink info versions implemented
+   :widths: 10 10 80
+
+   * - Name
+     - Type
+     - Description
+   * - ``fw``
+     - running
+     - Used to represent the firmware version.

Documentation/networking/devlink/index.rst

@@ -34,6 +34,7 @@ parameters, info versions, and other features it supports.
    :maxdepth: 1
 
    bnxt
+   hns3
    ionic
    ice
    mlx4