In my project I configure the kernel (2.6.32) in
We all know that kernel compiling and building takes few hours. Even for a small change, I'm compiling from scratch. So is there any way to compile and build only the changed file?
No, kernel compiling does not take “few hours”. Linus Torvalds said that it took him 12 minutes in the old days, and a lot less these days. Of course it depends whether you're compiling a kernel with just the drivers you need for your hardware, or a distribution kernel with all the drivers people may need — but even for a distribution kernel on a slightly elderly machine, it takes way less than an hour to do a full build.
Furthermore, if you change one file of the kernel, you don't need to do a full build. Just run
make modules if there are modules you need to recompile), and only the changed file (and the files that depend on it, if it's a header file) will be recompiled.