Hi Gaurab! Glad to hear you're interested in wine, and in cmd.
You might start by reading previous discussion on the topic, e.g. the full thread following http://www.winehq.org/pipermail/wine-devel/2009-December/080643.html and http://kegel.com/wine/sweng/2010/
Two tips that might help smooth your way: There is a lot of bison in wine already, so using bison might be the path of least resistance. Switching just one command to bison, while leaving the rest using the existing code, would likely be much easier to get committed than a big patch that changed lots of things.
Good luck! - Dan