looking at the reference manual for the i.MX28 (Figure 10-1. Logical Diagram of Clock Domains, Chapter 10 Clock Generation and Control (CLKCTRL), i.MX28 Applications Processor Reference Manual, Rev. 2, 08/2013) doesn't show the clock domain for the DC-DC.
So i created a little ASCII art accordingly to the diagramm in the RM:
Is it correct?