What all are the drivers those get compiled with the kernel?

There are numerous drivers present in the 'drivers' directory of Linux kernel. The kernel source for any Android mobile device [e.g. https://android.googlesource.com/kernel/msm/+/android-msm-2.6.35] is, too, not an exception. Definitely all the drivers are not relevant for the chipset which the mobile device is built on. It leads me to believe that *not* all the drivers which are present in the kernel source for a mobile device are built and shipped on commercial phones. Given the kernel source, how can one figure out what all are the drivers those get compiled for that particular mobile device? -- Thanks & Regards, Dipanjan