The 25-year-old, who left Bootham Crescent for the Robins last summer, has agreed a two-year deal with the League Two newcomers, with neither side revealing any details of a fee.
Smith, who cost the Robins £30,000, was transfer listed at the end of last season despite scoring three goals in 48 appearances.
The ex-Morecambe and Forest Green man played 43 times for York in 2010-11.
Source: BBC Sport
Source: FOOTYMAD