It's the core PMU. 
But PMU of ixp425 differs from XScale core PMU(ix. i80321)
About PMU of ixp425, cannot use generic registers of XScale core.

> Is this a peripheral PMU or the core PMU?  If it's the core PMU, it 
> should be the same as the generic XScale core PMU (used by i80200 and 
> i80321, for example), which is already described by xscalereg.h, right?