MIPS is Stanford’s alternative architecture to Berkeley’s RISC-I/RISC-II. I was somewhat concerned about their stuff in routers, especially when the primary bootloader used is proprietary.
The person that wrote the primary bootloader, is the same person writing most of the Mediatek kernel code in mainline. I forget where I put together their story, but I think they were some kind of prodigy type that reverse engineered and wrote an entire bootloader from scratch, implying a very deep understanding of the hardware. IIRC I may have seen that info years ago in the uboot forum. I think someone accused the mediatek bootloader of copying uboot. Again IIRC, their bootloader was being developed open source and there is some kind of partially available source still on a git somewhere. However, they wound up working for Mediatek and are now doing all the open source stuff. I found them on the OpenWRT and was a bit of an ass asking why they didn’t open source the bootloader code. After that, some of the more advanced users on OpenWRT explained to me how the bootloader is static, which I already kinda knew, I mean, I know it is on a flash memory chip on the SPI bus. This makes it much easier to monitor the starting state and what is really happening. These systems are very old 1990’s era designs, there is not a lot of room to do extra stuff unnoticed.
On the other hand, all cellular modems are completely undocumented, as are all WiFi modems since the early 2010’s, with the last open source WiFi modem being the Atheros chips.
There is no telling what is happening with cellular modems. I will say, the integrated nonremovable batteries have nothing to do with design or advancement. They are capable monitoring devices that cannot be turned off.
However, if we can monitor all registers in a fully documented SoC, we can fully monitor and control a peripheral bus in most instances.
Overall, I have little issue with Mediatek compared to Qualcomm. They are largely emulating the behavior of the bigger player, Broadcom.