Yes, that is what they are: SPL is the very very first thing the ARM chip boots, similar to the old BIOS that was at the front of your HDD? ARM Trusted Firmwa

Yes, that is what they are: SPL is the very very first thing the ARM chip boots, similar to the old BIOS that was at the front of your HDD? ARM Trusted Firmware roughly (VERY roughly) analogous to Intel's ME, it is a trusted execution environment for ARM