New EDL21 integration (#11325)

* New integration: edl21

* ✏️ Tweaks

* Update version number.

Co-authored-by: Franck Nijhof <frenck@frenck.nl>
Co-authored-by: Paulus Schoutsen <paulus@home-assistant.io>

source/_integrations/edl21.markdown

@@ -0,0 +1,37 @@
+---
+title: "EDL21 smart meter"
+description: "Instructions on how to integrate SML-based EDL21 smart meters into Home Assistant."
+ha_category:
+  - Sensor
+ha_release: 0.107
+---
+
+The `edl21` integration lets you read German EDL21 smart meters using [SML](https://de.wikipedia.org/wiki/Smart_Message_Language) from Home Assistant.
+
+In order to connect to the smart meter, an infrared transceiver is required.
+
+Compatible transceivers:
+
+- [DIY](https://wiki.volkszaehler.org/hardware/controllers/ir-schreib-lesekopf-rs232-ausgang)
+- [Weidmann Elektronik Schreib-/Lesekopf USB](https://shop.weidmann-elektronik.de/index.php?page=product&info=24)
+
+Tested smart meters:
+
+- Iskraemeco MT175 (ISKRA MT175-D2A51-V22-K0t)
+
+## Configuration
+
+To set it up, add the following information to your `configuration.yaml` file:
+
+```yaml
+sensor:
+  - platform: edl21
+    serial_port: /dev/ttyUSB0
+```
+
+{% configuration %}
+serial_port:
+  description: The device to communicate with. When using ser2net, use socket://host:port.
+  required: true
+  type: string
+{% endconfiguration %}