Adds documentation for the Yi Home Camera platform (#3580)

* Adding docs

* Various tweaks

* Fixed typos

source/_components/camera.yi.markdown

@@ -0,0 +1,96 @@
+---
+layout: page
+title: "Yi Home Camera"
+description: "Instructions on how to integrate a video feed (via FFmpeg) as a camera within Home Assistant."
+date: 2017-10-10 13:00
+sidebar: true
+comments: false
+sharing: true
+footer: true
+logo: yi.png
+ha_category: Camera
+ha_release: 0.56
+ha_iot_class: "Local Polling"
+---
+
+The `yi` camera platform allows you to utilize Yi Home Cameras within Home
+Assistant. Specifically, this platform supports the line of Yi Home Cameras
+that are based on the Hi3518e Chipset; these include:
+
+* Yi Home 17CN
+* Yi 1080p Home
+* Yi Dome
+* Yi 1080p Dome
+
+To successfully implement this platform, the Home Assistant host should be
+capable of multiple simultaneous reads; for every concurrent Home Assistant
+user, a connection will be made to the camera every 10 seconds.
+This should normally not be a problem.
+
+## {% linkable_title Preparing the Device %}
+
+### {% linkable_title Installing Alternative Firmware %}
+
+In order to integrate the camera with Home Assitant, it is necessary to install
+a custom firmware on the device. Instructions for doing so can be found via the
+[yi-hack-v3 GitHub project](https://github.com/shadow-1/yi-hack-v3).
+
+Once installed, please ensure that you have enabled FTP and Telnet on your
+device.
+
+<p class='note warning'>
+Some alternative Yi firmwares enable an experimental RTSP server, which will
+allow you to connect to your camera via other Home Assistant camera platforms.
+However, this RTSP server disables the ability to use the supremely-useful Yi
+Home app. In order to maintain both Home Assistant compatibility _and_ the native
+app, this platform retrieves videos via FTP.
+</p>
+
+### {% linkable_title Changing the FTP Password %}
+
+Once the custom firmware is installed, a password must be added to the FTP
+server. To do so:
+
+1. Telnet into your camera: `telnet <IP ADDRESS>`.
+2. Enter `root` as the username and `<blank>` as the password.
+3. Type `passwd` and hit `<Enter>`.
+4. Enter your new password twice.
+5. Log out of Telnet.
+
+## {% linkable_title Configuring the Platform %}
+
+To enable the platform, add the following lines to your
+`configuration.yaml` file:
+
+```yaml
+camera:
+  - platform: yi
+    host: '192.168.1.100'
+    password: my_password_123
+```
+
+Configuration variables:
+
+- **host** (*Required*): the IP address or hostname of the camera
+- **password** (*Required*): the password to the FTP server on the camera (from above)
+- **username** (*Optional*): the user that can access the FTP server (default: `root`)
+- **name** (*Optional*): a human-friendly name for the camera
+- **ffmpeg_arguments** (*Optional*): extra options to pass to `ffmpeg` (e.g. image quality or video filter options)
+
+## {% linkable_title Image quality %}
+
+Any option supported by the `ffmpeg` client can be utilized via the
+`ffmpeg_arguments` configuration parameter.
+
+One particularly useful adjustment deals with video size. Since Yi videos are
+fairly large (especially on the 1080p cameras), the following configuration will
+bring them down to a manageable size:
+
+```yaml
+camera:
+  - platform: yi
+    name: My Camera
+    host: '192.168.1.100'
+    password: my_password_123
+    ffmpeg_arguments: '-vf scale=800:450'
+```