Documentation for Application Credentials platform initial features

docs/config_entries_config_flow_handler.md

@@ -154,7 +154,7 @@ To get started, run `python3 -m script.scaffold config_flow_discovery` and follo
 
 Home Assistant has built-in support for integrations that offer account linking using [the OAuth2 authorization framework](https://tools.ietf.org/html/rfc6749). To be able to leverage this, you will need to structure your Python API library in a way that allows Home Assistant to be responsible for refreshing tokens. See our [API library guide](api_lib_index.md) on how to do this.
 
-The built-in OAuth2 support works out of the box with locally configured client ID / secret and with the Home Assistant Cloud Account Linking service. This service allows users to link their account with a centrally managed client ID/secret. If you want your integration to be part of this service, reach out to us at [hello@home-assistant.io](mailto:hello@home-assistant.io).
+The built-in OAuth2 support works out of the box with locally configured client ID / secret using the [Application Credentials platform](/docs/core/platform/application_credentials) and with the Home Assistant Cloud Account Linking service. This service allows users to link their account with a centrally managed client ID/secret. If you want your integration to be part of this service, reach out to us at [hello@home-assistant.io](mailto:hello@home-assistant.io).
 
 To get started, run `python3 -m script.scaffold config_flow_oauth2` and follow the instructions. This will create all the boilerplate necessary to configure your integration using OAuth2.
 

docs/core/platform/application_credentials.md

@@ -0,0 +1,52 @@
+---
+title: "Application Credentials"
+---
+
+Integrations may support [Configuration via OAuth2](/docs/config_entries_config_flow_handler#configuration-via-oauth2) allowing
+users to link their accounts. Integrations may add a `application_credentials.py` file and implement the functions described below.
+
+OAuth2 requires credentials that are shared between an application and provider. In Home Assistant, integration specific OAuth2 credentials are  provided using one or more approaches:
+
+- *Local OAuth with Application Credentials Component*: Users create their own credentials with the cloud provider, often acting as an application developer, and register the credentials with Home Assistant and integration. This approach is *required* by all integrations that support OAuth2.
+- *Cloud Account Linking with Cloud Component*: Nabu Casa registers credentials with the cloud provider, providing a seamless user experience. This approach provides a seamless user experience and is *recommended* ([more info](/docs/config_entries_config_flow_handler#configuration-via-oauth2)).
+
+## Adding support
+
+Integrations support application credentials with a file in the integration folder called `application_credentials.py` and implement the following:
+
+```python
+from homeassistant.core import HomeAssistant
+from homeassistant.components.application_credentials import AuthorizationServer
+
+
+async def async_get_authorization_server(
+    self, hass: HomeAssistant
+) -> AuthorizationServer:
+    """Return authorization server."""
+    return AuthorizationServer(
+        authorize_url="https://example.com/auth",
+        token_url="https://example.com/oauth2/v4/token"
+    )
+```
+
+### AuthorizationServer
+
+An `AuthorizationServer` represents the [OAuth2 Authorization server](https://datatracker.ietf.org/doc/html/rfc6749) used for an integration.
+
+| Name          | Type |                                                                                                    | Description |
+| ------------- | ---- | -------------------------------------------------------------------------------------------------- | ----------- |
+| authorize_url | str  | **Required** | The OAuth authorize URL that the user is redirected to during the configuration flow. |
+| token_url     | str  | **Required** | The URL used for obtaining an access token.                                           |
+
+## Import YAML credentials
+
+Credentials may be imported by integrations that used to accept YAML credentials using the import API `async_import_client_credential` provided by the application credentials integration.
+
+### ClientCredential
+
+A `ClientCredential` represents a client credential provided by the user.
+
+| Name          | Type |                                                                           | Description |
+| ------------- | ---- | ------------------------------------------------------------------------- | ----------- |
+| client_id     | str  | **Required** | The OAuth Client ID provided by the user.     |
+| client_secret | str  | **Required** | The OAuth Client Secret provided by the user. |