Add initial gardena bluetooth documentation (#27868)

Co-authored-by: Franck Nijhof <frenck@frenck.nl>

source/_integrations/gardena_bluetooth.markdown

@@ -0,0 +1,42 @@
+---
+title: Gardena Bluetooth
+description: Instructions on how to integrate Gardena Bluetooth devices within Home Assistant.
+ha_category:
+  - Binary Sensor
+  - Number
+  - Sensor
+  - Switch
+ha_release: '2023.8'
+ha_iot_class: Local Polling
+ha_codeowners:
+  - '@elupus'
+ha_domain: gardena_bluetooth
+ha_config_flow: true
+ha_platforms:
+  - binary_sensor
+  - number
+  - sensor
+  - switch
+---
+
+The Gardena Bluetooth integration allows users to integrate their [Gardena Smart](https://www.gardena.com/int/products/smart/) devices using Bluetooth into Home Assistant.
+
+The integration supports the [Water Control](#water-control) devices within Home Assistant:
+
+{% include integrations/config_flow.md %}
+
+## Water Control
+
+Allow control of the valve state of [Gardena Bluetooth Water Control](https://www.gardena.com/int/products/watering/water-controls/water-control-bluetooth) units.
+
+The paring of the device may require a [Factory Reset](#factory-reset) before it allows a connection.
+
+### Limitations
+
+- Control of offline scheduling settings is not supported.
+
+### Factory Reset
+
+1. Remove the battery.
+2. Push and hold Man. button and reinsert the battery.
+3. Hold the button for approx. 10 seconds.