monitor: Add a README

Add a README.md for fan monitor that provides a high level overview of
what it does.

Signed-off-by: Matt Spinler <spinler@us.ibm.com>
Change-Id: Id13ee104005d7328e3ba3102cf6d6f32ee3a1f78
diff --git a/README.md b/README.md
index 46e1379..21c5bb7 100755
--- a/README.md
+++ b/README.md
@@ -24,7 +24,7 @@
 file.*
 * Fan presence detection(presence)
   * The error logging feature is only available via the JSON configuration.
-* Fan monitoring(monitor)
+* [Fan monitoring(monitor)](monitor/README.md)
   * [JSON Documentation](monitor/json)
 * Fan control(control) - limited functionality
     * Currently only supports setting fans to the configured `full_speed`  
diff --git a/monitor/README.md b/monitor/README.md
new file mode 100644
index 0000000..0a607a3
--- /dev/null
+++ b/monitor/README.md
@@ -0,0 +1,17 @@
+# Fan Monitor
+
+The fan monitor application provides the following functionality:
+
+- Sets the functional state of fan sensors in the inventory based on comparing
+  the target speed of the sensor to the actual speed.
+- Sets the functional states of fan FRUs in the inventory based on the child
+  fan sensor functional states.
+- Creates event logs for fan sensors that have been nonfunctional for too long.
+- Creates event logs for fans that have been missing for too long.
+- Can power off the system based on rules that look at the number of
+  nonfunctional fan sensors or missing fans.
+
+This is all configurable in a [JSON file](json.md).  It also supports build
+time configuration based on a [YAML file](example/monitor.yaml), though that
+doesn't support the full functionality and has been deprecated in favor of the
+JSON configuration.