  A large class of two- and three-Higgs-doublet models with discrete symmetries
has been employed in the literature to address various aspects of flavor
physics. We analyse how the precision measurement of the Higgs to diphoton
signal strength would severely constrain these scenarios due to the
nondecoupling behavior of the charged scalars, to the extent that the number of
additional scalar doublets can be constrained no matter how heavy the
nonstandard scalars are. We demonstrate that if the scalar potential is endowed
with appropriate global continuous symmetries together with soft breaking
parameters, decoupling can be achieved thanks to the unitarity constraints on
the mass-square differences of the heavy scalars.
