YES

(VAR x y z)
(RULES
  f(+(x,y)) -> +(f(x),f(y))
  +(+(x,y),z) -> +(x,+(y,z))
)

(COMMENT
Termination is shown by KBO with weight

  w0 = 1
  w(+) = 0
  w(f) = 0

and precedence:

  f > +
)