Add a basic instruction

Author: dala318

components/devicies/index.rst

@@ -0,0 +1,67 @@
+Sub Device Configuration
+==================
+
+.. seo::
+    :description: Instructions for setting up sub devices in ESPHome.
+    :image: folder-open.svg
+
+ESPHome has support for createting sub devices in configuration where
+individual entities can be grouped to. The grouping has no direct effect
+on the functionality of the entities, but it can be used to group
+entities together in the Home Assistant UI. This is useful for
+example when you have a mix sensors on one device that are related to
+different physical devices.
+
+.. note::
+
+    Requires Home Assistant 2025.x or newer.
+
+.. _config-datetime:
+
+Base Sub Device Configuration
+---------------------------
+
+All devices in ESPHome have an id and name, and an optional suggested area.
+
+.. code-block:: yaml
+
+    # Example devices configuration
+    id: my_device
+    name: My Device
+
+    # Optional variables:
+    area: Living Room
+
+Configuration variables:
+
+- **id** (**Required**, string): Specify the ID for code generation.
+- **name** (**Required**, string): The name for the sub device.
+- **area** (*Optional*, string): The suggested area for the sub device.
+
+Assign entity to sub device
+----------
+
+For individual entities in your configuration, you can assign them to a
+sub device by using the ``device_id`` option. This is done by adding
+the ``device_id`` option to the entity configuration. The value should
+be the ID of the sub device you want to assign the entity to.
+
+.. code-block:: yaml
+
+    sensor:
+      - platform: template
+        # ...
+        device_id: my_device
+
+
+See Also
+--------
+
+- :doc:`esphome`
+- :ghedit:`Edit`
+
+.. toctree::
+    :maxdepth: 1
+    :glob:
+
+    *