As the other answers have eluded to, you need to check with the city or county. There are many places in the area that have Woodside addresses that are actually in Unincorporated San Mateo County. Subdividing in the Woodside area and the county can be very very challenging. The town of Woodside also has different lot size requirements depending where you are in the town. I would get the parcel number, determine if it is town or county, then go talk to the appropriate jurisdiction.
The rules here are different and you need to know what you can and can not do. Here is the website for the Town of Woodside, http://www.woodsidetown.org/building_division.html. This might help before you make a call. The Planning and Building Department counter hours are Monday - Friday 8:00am - 10:00am and 1:00pm - 3:00pm (Planning and Building Department phone number 650-851-6796)