The Customary Welcome to LQ, poovendhan.
On your 1st post as a newbie, you're inquiring about a specialised topic requiring hardware, firmware and software knowledge, worthy of a software dev, and hoping someone will write out a detailed explanation for you? You can't be a newbie and come up with a question like that. Where have you been?
Are you writing software? What are you trying to do? On what hardware?
How_To_Ask_a_Question
Have you searched this site? Kernel Documentation? Stackexchange? Google?
Winning cpu is likely the core/cpu that gets priority, i.e. whose irq is answered first, as there's only one databus.