/* Initialize Environment and Download source */
https://source.android.com/source/building-kernels.html

/* Download specific kernel */
git clone https://android.googlesource.com/kernel/msm.git

*** when download is finished, you will have an empty directory until you checkout something ***

/* list branches available */
git branch -a
git branch -a –contains <commit>

/* checkout what you are after (a specific branch and/or a specific build/commit) */
git checkout <commit>

/* Grab  Cross Compiler */
git clone https://android.googlesource.com/platform/prebuilts/gcc/linux-x86/arm/arm-eabi-4.6

/* add toolchain to your PATH */

*** my preference is to add it to bashrc ***

*** dirty issue, the kernel will append -dirty to the build. To get rid of that **
Modify include/config/kernel.release

*** modify Makefile ***
add configuration flag to setlocalversion to get rid of the dirty issue
–save-scmversion

*** example ***
$(Q)echo “$(KERNELVERSION)$$($(CONFIG_SHELL) $(srctree)/scripts/setlocalversion –save-scmversion $(srctree))” > $@

/** Prepare for building */

*** if you are building for a specific device, or want module support ***
** modify Makefile **
EXTRAVERSION
Add compiler option flag -fno-pic