Sorry for the late response. I got busy in other things.
I looked at the Galileo 2 schematic and it seems that ADC has a direct SPI interface to the SoC. The sample clock and the data out of the TI ADC chip directly interface to SPI0 ports of the SoC. Upon reviewing the TI data sheet for the ADC chip it seems to me that it can very well sample at 1 million samples per second (1MSPS). That is the the sample clock from the SoC can be up to 1MHz. Since the SoC runs at 400+MHz it seems technically possible to access the ADC samples at 1MSPS rate. The only thing I am not sure of is how I can control this though Arduino SPI environment? I am wiling to write my own custom library if I can find enough documentation on this subject.
Thanks for any help.
VIpin