Update README.buildsystem.md with pictorial representation of SONiC Build execution sequence

README.buildsystem.md

@@ -62,6 +62,12 @@ Every **platform/[VENDOR]/** directory is a derived part of buildimage frontend,
 ### Build output
 **target/** is basically a build output. You can find all build artifacts there.  
 
+### SONiC Build Execution sequence
+A pictorial representation depicting the control flow during build execution sequence is shown as below,
+
+![image](./images/sonic_build_execution_sequence.png)
+
+
 ## Recipes and target groups
 Now let's go over a definition of recipes and target groups.  
 **Recipe** is a small makefile that defines a target and set of variables for building it.

platform/vs/README.vsdocker.md

@@ -1,6 +1,29 @@
 HOWTO Use Virtual Switch (Docker)
 
+**Steps for Docker Virtual Switch Image readiness:**
+
+   Option 1: Generate the image from source, using following commands.
+   ```   
+             Step1: Clone SONiC Source Repository
+                    $ git clone https://github.com/sonic-net/sonic-buildimage.git
+
+             Step2: Load the overlay module. 
+                    $ sudo modproble overlay
+                    $ cd sonic-buildimage/
+
+             Step3: Initialize the Build system to fetch all dependent component source and packages, recursively. 
+                    $ make init
+
+             Step4: Configure the Build system to VS platform
+                    $ make configure PLATFORM=vs
+
+             Step5: Start the Build Process to generate Docker Virtual Switch Image
+                    $ make target/docker-sonic-vs.gz
+   ```
+   Option 2: Download the image directly from Community builds link.
 
+
+**Steps for Docker Virtual Switch Image usage:**
 1. Create a docker with two front panel ports
 
 ```
@@ -11,13 +34,17 @@ sw-srv1 (id: 6)
 sw-srv0 (id: 5)
 ```
 
-2. Start sonic virtual switch docker
+2. Load the built/downloaded Docker Virtual Switch image in the Host machine
+```
+$ docker load -i docker-sonic-vs.gz
+```
 
+3. Start sonic virtual switch docker
 ```
 $ docker run --privileged --network container:sw --name vs -d docker-sonic-vs
 ```
 
-3. Setup IP in the virtual switch docker
+4. Setup IP in the virtual switch docker
 
 ```
 $ docker exec -it vs bash
@@ -27,7 +54,7 @@ root@2e9b5c2dc2a2:/# config interface startup Ethernet0
 root@2e9b5c2dc2a2:/# config interface startup Ethernet4
 ```
 
-4. Setup IP in the server network namespace
+5. Setup IP in the server network namespace
 
 ```
 $ sudo ip netns exec sw-srv0 ifconfig eth0 10.0.0.1/31
@@ -36,7 +63,7 @@ $ sudo ip netns exec sw-srv1 ifconfig eth0 10.0.0.3/31
 $ sudo ip netns exec sw-srv1 ip route add default via 10.0.0.2
 ```
 
-5. Ping from sw-srv0 to sw-srv1
+6. Ping from sw-srv0 to sw-srv1
 
 ```
 $ sudo ip netns exec sw-srv0 ping  10.0.0.3