Adding architecture details

Author: murali-reddy

Documentation/README.md

@@ -8,6 +8,28 @@ Kube-router consists of 3 core controllers and multiple watchers as depicted in
 
 ![Arch](./img/kube-router-arch.png)
 
+Each of the [controller](https://github.com/cloudnativelabs/kube-router/tree/master/app/controllers) follows below structure
+
+```
+func Run() {
+    for {
+        Sync() // control loop that runs for ever and perfom sync at periodic interval
+    }
+}
+
+func OnUpdate() {
+    Sync() // on receiving update of a watched API object (namespace, node, pod, network policy etc)
+}
+
+Sync() {
+    //re-concile any state changes
+}
+
+Cleanup() {
+    // cleanup any changes (to iptables, ipvs, network etc) done to the system
+}
+```
+
 ## See Kube-router in action
 
 #### Network Services Controller