Add entity registry

docs/entity_registry_index.md

@@ -0,0 +1,22 @@
+---
+title: Entity Registry
+sidebar_label: Introduction
+---
+
+The entity registry is a registry where Home Assistant keeps track of entities. Any entity that is added to Home Assistant and having a unique ID will be registered in the registry.
+
+Being registered has the advantage that the same entity will always get the same entity ID. It will also prevent other entities from using that entity ID.
+
+A user is also able to override the name of an entity in the entity registry. When set, the name of the entity registry is used in favor of the name the device might give itself.
+
+## Unique ID requirements
+
+An entity is looked up in the registry based on a combination of domain (ie `light`), platform name (ie `hue`) and the unique ID of the entity. It is therefore very important that the unique ID is unique! It is also important that it is not possible for the user to change the unique ID, because that means it will lose all its settings related to it.
+
+Good sources for a unique ID:
+
+ - Serial number of a device
+ - MAC address of a device
+ - latitude/longitude
+
+If a device has a single serial but provides multiple entities, combine the serial with unique identifiers for the entities. For example, if a device measures both temperature and humidithy, you can uniqueley identify the entities using `{serial}-{sensor_type}`.

website/i18n/en.json

@@ -46,6 +46,7 @@
     "development_submitting": "Submit your work",
     "development_testing": "Testing your code",
     "development_validation": "Validate the input",
+    "entity_registry_index": "Entity Registry",
     "external_api_rest_python": "REST API - Python bindings",
     "external_api_rest": "RESTful API",
     "external_api_server_sent_events": "Server-sent events",
@@ -82,6 +83,7 @@
     "Configuration.yaml": "Configuration.yaml",
     "Config Entries": "Config Entries",
     "Data Entry Flow": "Data Entry Flow",
+    "Entity Registry": "Entity Registry",
     "Developing a feature": "Developing a feature",
     "Development 101": "Development 101",
     "Creating Platforms": "Creating Platforms",

website/sidebars.json

@@ -15,6 +15,9 @@
     ],
     "Data Entry Flow": [
       "data_entry_flow_index"
+    ],
+    "Entity Registry": [
+      "entity_registry_index"
     ]
   },
   "Extending Frontend": {