Secondary Program Loader, typically, a second stage bootloader. Not a term actually used by Qualcomm for msm7k has a more complex boot path involving both CPUs. Initial/secondary program loader is usually in reference to nand/onenand boot setups where you have a very small initial bootloader (1k to 16k typical), that is just enough to load a much larger secondary bootloader. Often there is something that runs first, in-rom, on-die (this is true of omap and msm chips for example) that is responsible for getting the IPL loaded.
