supported-technologies/matter: Add initial Matter support docs

A short description on Matter and the current status on our integration
work in Oniro.

Closes: eclipse/oniro-core/docs#7



Signed-off-by: Stefan Schmidt <stefan.schmidt@huawei.com>

docs/index.rst

@@ -35,6 +35,7 @@ Build System Guide
    :maxdepth: 2
 
    supported-technologies/openthread
+   supported-technologies/matter
    supported-technologies/containers
    supported-technologies/modbus
    supported-technologies/lvgl

docs/supported-technologies/matter.rst

+.. SPDX-FileCopyrightText: Huawei Inc.
+..
+.. SPDX-License-Identifier: CC-BY-4.0
+
+Matter
+######
+
+The Matter protocol (formerly Project Connected Home over IP, CHIP) is an
+application layer protocol for IoT devices and controllers. It is based on IPv6
+and UDP/TCP and describes the message format, security, interaction model and
+data model among other things. Matter is a new standard with its first release
+in September 2022. For more details on Matter, `Click <https://csa-iot.org/all-solutions/matter/>`__.
+
+Matter support in Oniro
+***********************
+
+The Matter working group has developed an `open-source SDK
+<https://github.com/project-chip/connectedhomeip>`__  for Matter in tandem
+with the specification. This reference implementation has been used for all
+testing events towards the final protocol.
+
+To support Matter in Oniro, we integrated the Matter open-source SDK in our build
+with a Yocto recipe that builds the 1.0 release of the SDK. In the future we will
+follow the release branch that backports fixes for 1.0.x until there will be a
+formal 1.1 release.
+
+So far this work has been focused on the Linux flavour. The Matter core
+components, libraries and a few examples are working. No work has been done on
+the Zephyr flavour yet, but it is on the Oniro roadmap to support Matter on
+Zephyr as well.
+
+Matter is not part of the default images provided by Oniro. To add it to your
+custom image, you would need to add it to the image recipe, or append
+it in your `local.conf` to every image you build e.g.:
+
+.. code-block:: console
+
+        IMAGE_INSTALL:append = " matter"