As I understand it, and I am not a kernel expert, the existing real time patches reduced latency to improve the soft real time responsiveness of the system, but

As I understand it, and I am not a kernel expert, the existing real time patches reduced latency to improve the soft real time responsiveness of the system, but were still priority based. The Ericsson patch appears to be closer to the idea of hard real time, i.e. that scheduled events have a fixed deadline that must be met.