In a broad sense, dogo refers to 'specific small local clans' as opposed to large regional clans which control wide territories.
Dogo is a historical term that frequently appears in relation to the Muromachi period and the Sengoku Period (Period of Warring States) but when used in reference to the period of Yamato dynasty, it refers to kuninomiyatsuko (provincial governor) class of local heads.
The following mainly pertains to dogo in Japan particularly during the middle ages.
Ancient sources refer to them as 'jizamurai' or 'myoji no hyakusho' (farmers with surnames). It means that they were low-ranking samurai who served as both warriors and farmers. As the separation of farmers and samurai took place, weaker samurai families came to be called 'dogo' (narrow sense).
Those including the lords of manors of Jizamurai
In wider sense, while larger gozoku (local ruling families) had a large power to reign some counties in his assigned region whether he stayed in the center or the local, dogo was a retainer or hikan (low-level bureaucrat) of jito, who were usually smaller gozoku and reigned some villages which were under control of or independent from the larger gozoku, or kokujin ryoshu (local samurai lord) of the jito's linage, and even included zaichi-ryoshu (local lord) which was to be the main stream of jizamurai.