what happens when we merge 2 patches in case of drivers?

Case 1: if patch one has c,d,g drivers and patch 2 has u driver,then resultant driver is
  u_merged.drv

Case 2:if patch one has c,d,g drivers and patch 2 has only c driver,then resultant drivers are

c_merged.drv
d_merged.drv
g_merged.drv