This document describes how to use U-Boot on the Broadcom Northstar boards, comprised of the Cortex A9 ARM-based BCM470x and BCM5301x SoCs. These were introduced in 2012-2013 and some of them are also called StrataGX.
Northstar is part of the iProc SoC family.
A good overview of these boards can be found in Jon Mason's presentation "Enabling New Hardware in U-Boot" where the difference between Northstar and Northstar Plus and Northstar 2 (Aarch64) is addressed.
The ROM in the Northstar SoC will typically look into NOR flash memory for a boot loader, and the way this works is undocumented. It should be possible to execute U-Boot as the first binary from the NOR flash but this usage path is unexplored. Please add information if you know more.
When we use U-Boot with D-Link routers, the NOR flash has a boot loader and web server that can re-flash the bigger NAND flash memory for object code in the SEAMA format, so on these platforms U-Boot is converted into a SEAMA binary and installed in the SoC using the flash tool resident in the NOR flash. Details can be found in the OpenWrt project codebase.
$ make CROSS_COMPILE=${CROSS_COMPILE} bcmns_defconfig$ make CROSS_COMPILE=${CROSS_COMPILE}
$ ${CROSS_COMPILE}strip u-boot