Serial HyperLink Sideband Signals function

There is hyperlink interface found in most of Keystone processors. This interface contains signals such as Tx,Rx, Clk and sideband signals such as MCMRXFLCLK, MCMRXFLDAT,MCMTXFLCLK etc. Can someone tell me what are these sideband signals are to do in this interface? Is there any document which describes the signals of hyperlink interface?

Thanks

Sachin