Merge pull request #1171 from allenporter/camera-webrtc

Update developer docs to mention RTSP to WebRTC

docs/core/entity/camera.md

@@ -91,6 +91,25 @@ class MyCamera(Camera):
         """Handle the WebRTC offer and return an answer."""
 ```
 
+### RTSP to WebRTC
+
+An integration may provide a WebRTC stream for any RTSP camera using `async_register_rtsp_to_web_rtc_provider`. The current best practice is for an integration to provide the actual stream manipulation with an Add-on or external service.
+
+
+```python
+async def handle_offer(stream_source: str, offer_sdp: str) -> str:
+    """Handle the signal path for a WebRTC stream and return an answer."""
+    try:
+        return await client.offer(offer_sdp, stream_source)
+    except ClientError as err:
+        raise HomeAssistantError from err
+
+# Call unsub() when integration unloads
+unsub = camera.async_register_rtsp_to_web_rtc_provider(
+    hass, DOMAIN, handle_offer
+)
+```
+
 ### Turn on
 
 ```python