Any good reference for Runtime suspend and resume

Hi all, I was trying to understand how runtime suspend and resume is implemented in the mmc subsystem. It would be very greatful if somebody can give good reference to understand the call stack, and sequence of runtime_suspend, claim_host, release_host operations execution. I was trying to findout good docs for mmc/SD subsystem docs but no help. -- With regards, Sandeep Kumar Anantapalli,