Update docs for newer devices and DeviceConfig (#614)

* Update docs for newer devices and DeviceConfig

* Tweak docs post review

* Move sentence to newline

* Update post review

* Update following review

docs/source/discover.rst

@@ -1,9 +1,59 @@
+.. py:module:: kasa.discover
+
 Discovering devices
 ===================
 
 .. contents:: Contents
    :local:
 
+Discovery
+*********
+
+Discovery works by sending broadcast UDP packets to two known TP-link discovery ports, 9999 and 20002.
+Port 9999 is used for legacy devices that do not use strong encryption and 20002 is for newer devices that use different
+levels of encryption.
+If a device uses port 20002 for discovery you will obtain some basic information from the device via discovery, but you
+will need to await :func:`SmartDevice.update() <kasa.SmartDevice.update()>` to get full device information.
+Credentials will most likely be required for port 20002 devices although if the device has never been connected to the tplink
+cloud it may work without credentials.
+
+To query or update the device requires authentication via :class:`Credentials <kasa.Credentials>` and if this is invalid or not provided it
+will raise an :class:`AuthenticationException <kasa.AuthenticationException>`.
+
+If discovery encounters an unsupported device when calling via :meth:`Discover.discover_single() <kasa.Discover.discover_single>`
+it will raise a :class:`UnsupportedDeviceException  <kasa.UnsupportedDeviceException>`.
+If discovery encounters a device when calling :meth:`Discover.discover() <kasa.Discover.discover>`,
+you can provide a callback to the ``on_unsupported`` parameter
+to handle these.
+
+Example:
+
+.. code-block:: python
+
+    import asyncio
+    from kasa import Discover, Credentials
+
+    async def main():
+        device = await Discover.discover_single(
+            "127.0.0.1",
+            credentials=Credentials("myusername", "mypassword"),
+            discovery_timeout=10
+        )
+
+        await device.update()  # Request the update
+        print(device.alias)  # Print out the alias
+
+        devices = await Discover.discover(
+            credentials=Credentials("myusername", "mypassword"),
+            discovery_timeout=10
+        )
+        for ip, device in devices.items():
+            await device.update()
+            print(device.alias)
+
+    if __name__ == "__main__":
+        asyncio.run(main())
+
 API documentation
 *****************