If you have the rest of the motherboard markings - the letters and numbers before the "rev:a2," you can google the motherboard number to find links to your motherboard manufacturer. You should be able to find the drivers on that site.
If you are looking only for Realtek drivers, you can find them here
. If you have a motherboard less than two years old get the HD drivers, if it is older, get the AC97 driver.