Yield pattern of infill panel is the pattern along which failure of the panel is expected to occur. It will be as in the case of RC slab, if it is an RC panel. But for masonry infill panel, it will be slightly different depending on relative strengths of masonry units and mortar used.
Since you are probably dealing with the modelling aspect, this may serve as a good read!
The term 'yield pattern' is a misnomer because most infills (except steel clads) do not 'yield'. However, in the literature, when the infill is subject to out-of-plane (ressure) loading, it is described as exhibiting failure path similar to the yield line theory in plates. Under inplane loading, these infills fail due to diagonal compression strut mechanism and is affected by the retaive stiffness of the surrounding frame and that of the infill.