For each arch has its own directory in  /arch

For example, for arm architecture, the source code will located in /arch/arm

In this folder, there are common folders and MCU specific folders.

1. common folders:
   boot, common, configs, kernel, lib, mm, nwfpe, vfp, oprofile, tools
2. MCU specific folders:
   mach-XXXX – for example mach-omap2 is for TI OMAP mpus
3. Share code for multiple MCUs
   plat-XXXX – for example, common code of omap/omap2 will be located in plat-omap