Add serial sensor docs (home-assistant#3619)

source/_components/sensor.serial.markdown

@@ -0,0 +1,55 @@
+---
+layout: page
+title: "Serial Sensor"
+description: "Instructions how to integrate data from serial connected sensors into Home Assistant."
+date: 2017-10-13 07:00
+sidebar: true
+comments: false
+sharing: true
+footer: true
+logo: home-assistant.png
+ha_category: Sensor
+ha_release: 0.56
+ha_iot_class: "Local Polling"
+---
+
+The `serial` sensor platform is using the data provided by a device connected to the serial port of the system where Home Assistant is running. With [`ser2net`](http://ser2net.sourceforge.net/) and [`socat`](http://www.dest-unreach.org/socat/) would it also work for sensors connected to a remote system.
+
+To check what kind of data is arriving at your serial port, use a command-line tool like `minicom` or `picocom` on Linux, on a macOS you can use `screen` or on Windows `putty`. 
+
+```bash
+$ sudo minicom -D /dev/ttyACM0
+```
+
+To setup a serial sensor to your installation, add the following to your `configuration.yaml` file:
+
+```yaml
+# Example configuration.yaml entry
+sensor:
+  - platform: serial
+    port: /dev/ttyACM0
+```
+
+{% configuration %}
+  port:
+    description: Local serial port where the sensor is connected and access is granted.
+    required: true
+    type: string
+  name:
+    description: Friendly name to use for the frontend. Default to "Serial sensor".
+    required: false
+    type: string
+{% endconfiguration %}
+
+
+## {% linkable_title `value_template` for Template sensor %}
+
+### {% linkable_title TMP36 %}
+
+{% raw %}
+```yaml
+"{{ (((states('sensor.serial_sensor') | float * 5 / 1024 ) - 0.5) * 100) | round(1) }}"
+```
+{% endraw %}
+
+