You might have come across some pieces I've written recently on the ARMv7 architecture.
Navigating the Cortex Maze
ARMv7-A - Power to the People
ARMv6-M vs ARMv7-M - Unpacking the Microcontrollers
I've just published the final side of the triangle on ARMv7-R. Check out ARMv7-R - Hidden Power. The ARMv7-R architecture doesn't get the headlines in the same way as ARMv7-A and ARMv7-M but it is an incredibly important part of the story, meeting key requirements for very specialised hard real-time systems.
And don't forget yesterday's announcement of the ARMv8-R architecture (ARMv8-R, architecture innovation for embedded systems) the next step in the evolution. You can learn a lot more about that at TechCon (ARM at ARM TechCon) next week in Santa Clara.
Impressive set of reference material. Thanks Chris!