Updated the developer documentation

source/developers/add_new_platform.markdown

@@ -0,0 +1,25 @@
+---
+layout: page
+title: "Adding support for a new platform"
+date: 2014-12-21 13:27
+sidebar: false
+comments: true
+sharing: true
+footer: true
+---
+
+Components that interact with devices are structured in core- and platform logic. This allows the same logic to be used for different platforms.
+
+For example, the built-in `switch` component consists of the following files in [`homeassistant/components/switch/`](https://github.com/balloob/home-assistant/tree/master/homeassistant/components/switch):
+
+| File | Description |
+| ---- | ----------- |
+| \_\_init\_\_.py | Contains the Switch core logic.|
+| wemo.py | WeMo platform logic. Included if in config `platform=wemo`. |
+| tellstick.py | Tellstick platform logic. Included if in config `platform=tellstick`. |
+
+If you are planning to add support for a new type of device to an existing component, you can get away with only writing platform logic. Have a look at how the component works with other platforms and create a similar file for the platform that you would like to add.
+
+<div class='note'><p class='title'>Note</p><p class='content'>
+Platform logic should not interface directly with the devices but use a third-party Python 3 library that speaks the actual API.
+</p></div>