Dev docs for config entry options (#185)

* Dev docs for config entry options

docs/config_entries_index.md

@@ -3,7 +3,7 @@ title: Config Entries
 sidebar_label: Introduction
 ---
 
-Config Entries are configuration data that are persistently stored by Home Assistant. A config entry is created by a user via the UI. The UI flow is powered by a [config flow handler](config_entries_config_flow_handler.md) as defined by the component.
+Config Entries are configuration data that are persistently stored by Home Assistant. A config entry is created by a user via the UI. The UI flow is powered by a [config flow handler](config_entries_config_flow_handler.md) as defined by the component. Config entries can also have an extra [options flow handler](config_entries_options_flow_handler.md), also defined by the component.
 
 ## Setting up an entry
 

docs/config_entries_options_flow_handler.md

@@ -0,0 +1,40 @@
+---
+title: Options Flow Handlers
+---
+
+Config Entry Options uses the [Data Flow Entry framework](data_entry_flow_index.md) to allow users to update a config entries options. Components that want to support config entry options will need to define a Options Flow Handler.
+
+## Options support
+
+For a component to support options it needs to have an `async_get_options_flow` method in its config flow handler. Calling it will return an instance of the components options flow handler.
+
+```python
+@staticmethod
+@callback
+def async_get_options_flow(config, options):
+    return OptionsFlowHandler(config, options)
+```
+
+## Flow handler
+
+The Flow handler works just like the config flow handler, except that the first step in the flow will always be `async_step_init`.
+
+```python
+class OptionsFlowHandler(data_entry_flow.FlowHandler):
+    def __init__(self, config, options):
+```
+
+## Signal updates
+
+If the component should act on updated options, you can register an update listener to the config entry that will be called when the entry is updated.
+
+```python
+entry.add_update_listener(update_listener)
+```
+
+The Listener shall be an async function that takes the same input as async_setup_entry. Options can then be accessed from `entry.options`.
+
+```python
+async def update_listener(hass, entry):
+```
+

website/sidebars.json

@@ -36,7 +36,8 @@
     ],
     "Config Entries": [
       "config_entries_index",
-      "config_entries_config_flow_handler"
+      "config_entries_config_flow_handler",
+      "config_entries_options_flow_handler"
     ],
     "Data Entry Flow": [
       "data_entry_flow_index"