This is about building the latest Kernel / 3.10 for RPi. Bleeding Edge.

Preperations

sudo apt-get install git libncurses5 libncurses5-dev qt4-dev-tools qt4-qmake pkg-config build-essential gcc-arm-linux-gnueabi bc  
# NEEDS BC!!!!

Clone Stuff

mkdir rpi_kernel_10  
cd rpi_kernel_10  
git clone https://github.com/raspberrypi/tools.git  
git clone https://github.com/raspberrypi/linux.git  
cd ~/rpi_kernel_10/linux/.git  
git branch -a  
cd ~/rpi_kernel_10/linux  
git checkout -t -b rpi-3.10.y remotes/origin/rpi-3.10.y  
git pull  
cd ~/rpi_kernel_10  
git clone https://github.com/raspberrypi/firmware.git  
cd ~/rpi_kernel_10/firmware/.git  
git branch -a  
cd ~/rpi_kernel_10/firmware  
git checkout -t -b next remotes/origin/next  
git pull  
cd ~/rpi_kernel_10

Make Kernel

cd linux  
make mrproper  
mkdir ../kernel  
# Kernel Types  
# find . -name \*bcmrpi\*config -print  
# ./arch/arm/configs/bcmrpi_emergency_defconfig  
# ./arch/arm/configs/bcmrpi_defconfig  
# ./arch/arm/configs/bcmrpi_cutdown_defconfig  
make O=../kernel/ ARCH=arm CROSS_COMPILE=/usr/bin/arm-linux-gnueabi- bcmrpi_defconfig  
make O=../kernel/ ARCH=arm CROSS_COMPILE=/usr/bin/arm-linux-gnueabi- menuconfig #xconfig  
#Device Drivers->Input Device Support->TouchScreens->USB Touchscreen Driver (Build it into or as module, check if eGalax here!)  
make O=../kernel/ ARCH=arm CROSS_COMPILE=/usr/bin/arm-linux-gnueabi- -k -j3  
cd ../  
cd tools/mkimage  
./imagetool-uncompressed.py ../../kernel/arch/arm/boot/Image  
cd ../../

Make Modules

cd kernel  
mkdir ../modules/  
make modules_install ARCH=arm CROSS_COMPILE=/usr/bin/arm-linux-gnueabi- INSTALL_MOD_PATH=../modules/

Install Kernel on existing RPi SD Card / Raspbian

# mount sdcard in your Ubuntu (I made an folder sdb1 for boot partiton and sdb2 for the root partition)  
cd ~  
mkdir sdb1 sdb2  
mount /dev/sdb1 sdb1  
mount /dev/sdb2 sdb2

# boot partition  
#replace /sdb1/boot/bootcode.bin with rpi_kernel_10/firmware/boot/bootcode.bin  
sudo rm ~/sdb1/bootcode.bin  
cp ~/rpi_kernel_10/firmware/boot/bootcode.bin ~/sdb1/  
#replace /sdb1/boot/kernel.img with the previously created kernel image  
sudo rm ~/sdb1/kernel.img  
cp ~/rpi_kernel_10/tools/mkimage/kernel.img ~/sdb1/  
#replace /sdb1/boot/start.elf with rpi_kernel_10/firmware/boot/start.elf  
sudo rm ~/sdb1/start.elf  
cp ~/rpi_kernel_10/firmware/boot/start.elf ~/sdb1/

# root partition  
#replace /sdb2/lib/firmware with <modules_builded_above_folder>/lib/firmware  
sudo rm -rf ~/sdb2/lib/firmware/  
sudo cp -a ~/rpi_kernel_10/modules/lib/firmware/ ~/sdb2/lib/  
#replace /sdb2/lib/modules with <modules_builded_above_folder>/lib/modules  
sudo rm -rf ~/sdb2/lib/modules/  
sudo cp -a ~/rpi_kernel_10/modules/lib/modules/ ~/sdb2/lib/  
#replace /sdb2/opt/vc with firmware-next/hardfp/opt/vc/  
sudo rm -rf ~/sdb2/opt/vc  
sudo cp -a ~/rpi_kernel_10/firmware/hardfp/opt/vc/ ~/sdb2/opt/

# sync usb mount  
sync

# Unmount sdcard  
cd ~  
umount sdb1  
umount sdb2

Boot Pi and calibrate Touchscreen

This stuff happens on the Pi!

Preperations

sudo apt-get install libx11-dev libxext-dev libxi-dev x11proto-input-dev

Install Tool / xinput_calibrator

cd ~  
wget http://github.com/downloads/tias/xinput_calibrator/xinput_calibrator-0.7.5.tar.gz  
tar -xvzf xinput_calibrator-0.7.5.tar.gz  
cd xinput_calibrator-0.7.5  
./configure  
make  
sudo make install

Calibrate (in Xserver, so open Terminal while beeing in Graphical User Mode)

xinput_calibrator

It will give output like this:

Calibrating EVDEV driver for "eGalax Inc. USB TouchController" id=8  
current calibration values (from XInput): min_x=1938, max_x=114 and min_y=1745, max_y=341
Doing dynamic recalibration:  
Setting new calibration data: 121, 1917, 317, 1741  
--> Making the calibration permanent <--

copy the snippet below into ‘/etc/X11/xorg.conf.d/99-calibration.conf’

Section "InputClass"  
Identifier "calibration"  
MatchProduct "eGalax Inc. USB TouchController"  
Option "Calibration" "121 1917 317 1741"  
Option "SwapAxes" "1"  
EndSection

Use the Output after “–> Making the calibration permanent <–
copy the snippet below into ‘/etc/X11/xorg.conf.d/99-calibration.conf’”
And copy the part after that into following file:

sudo mkdir /etc/X11/xorg.conf.d  
sudo vi /etc/X11/xorg.conf.d/01-input.conf

After that, save, exit and reboot.
That should conclude your newly “Custom baked Kernel” and your EGalax Touchscreen Support.

Thanks a lot to http://engineering-diy.blogspot.de/2013/01/adding-7inch-display-with-touchscreen.html http://mitchtech.net/raspberry-pi-kernel-compile/ - Raspberry Pi Kernel Compile
and http://karuppuswamy.com/wordpress/2013/01/17/how-to-get-evtouch-touch-screen-kit-working-in-linux/
from which I learnt and borrowed most of the stuff and tips and rewrote this How To with minor changes

Upgrade

cd linux  
make mrproper  
git pull  
cd ../tools  
git pull  
cd ../firmware  
git pull