BCM2837
Build Kernel(N900)
Tooolchain
$ git clone https://github.com/raspberrypi/tools $ sudo mv tools /opt/pi3 $ export PATH=$PATH:/opt/pi3/arm-bcm2708/arm-bcm2708-linux-gnueabi/bin/
Build Kernel
$ git clone --depth=1 https://github.com/raspberrypi/linux $ cd linux $ KERNEL=kernel7 $ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- bcm2709_defconfig $ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- zImage modules dtbs
With sdb1 being the FAT (boot) partition, and sdb2 being the ext4 filesystem (root) partition.
$ mkdir mnt/fat32 $ mkdir mnt/ext4 $ sudo mount /dev/sdb1 mnt/fat32 $ sudo mount /dev/sdb2 mnt/ext4 $ sudo make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- INSTALL_MOD_PATH=mnt/ext4 modules_install $ sudo cp mnt/fat32/$KERNEL.img mnt/fat32/$KERNEL-backup.img $ sudo scripts/mkknlimg arch/arm/boot/zImage mnt/fat32/$KERNEL.img $ sudo cp arch/arm/boot/dts/*.dtb mnt/fat32/ $ sudo cp arch/arm/boot/dts/overlays/*.dtb* mnt/fat32/overlays/ $ sudo cp arch/arm/boot/dts/overlays/README mnt/fat32/overlays/ $ sudo umount mnt/fat32 $ sudo umount mnt/ext4
Enable UART output for pi3
$ nano mnt/fat32/config.txt dtoverlay=pi3-miniuart-bt force_turbo=1