Ashutosh,
I have a number of blog posts with sample code for the two types of SDK handlers that are supported (div handler and sapui5 handler).
Most can be found from this post:
Design Studio 1.2/1.3 SDK - Design Studio Utility Pack
The correct way to extend an SAPUI5 component is illustrated in the SuperImage post:
But I'd encourage you to take a look at the code in all the others, too - As it may help.
Hope this helps!