The design consists in the features of shape and configuration of the LUMINAIRE MOUNTING INTERFACE as shown in the drawings.Figure 1 is a top perspective view of a luminaire mounting interface in accordance with a first variant of the present design;Figure 2 is a bottom perspective view of the luminaire mounting interface of Figure 1;Figure 3 is a top plan view of the luminaire mounting interface of Figure 1;Figure 4 is a front elevation view of the luminaire mounting interface of Figure 1;Figure 5 is a side elevation view of the luminaire mounting interface of Figure 1, the opposite side being a mirror image thereof;Figure 6 is a bottom plan view of the luminaire mounting interface of Figure 1;Figure 7 is a rear elevation view of the luminaire mounting interface of Figure 1;Figure 8 is a plan view of the mounting interface of the luminaire mounting interface of Figure 1;Figure 9 is a top perspective view of a luminaire mounting interface in accordance with a second variant of the present design;Figure 10 is a bottom perspective view of the luminaire mounting interface of Figure 9;Figure 11 is a top plan view of the luminaire mounting interface of Figure 9;Figure 12 is a front elevation view of the luminaire mounting interface of Figure 9;Figure 13 is a side elevation view of the luminaire mounting interface of Figure 9, the opposite side being a mirror image thereof;Figure 14 is a bottom plan view of the luminaire mounting interface of Figure 9;Figure 15 is a rear elevation view of the luminaire mounting interface of Figure 9;Figure 16 is a plan view of the mounting interface of the luminaire mounting interface of Figure 9;Figure 17 is a top perspective view of a luminaire mounting interface in accordance with a third variant of the present design;Figure 18 is a bottom perspective view of the luminaire mounting interface of Figure 17;Figure 19 is a top plan view of the luminaire mounting interface of Figure 17;Figure 20 is a front elevation view of the luminaire mounting interface of Figure 17;Figure 21 is a side elevation view of the luminaire mounting interface of Figure 17, the opposite side being a mirror image thereof;Figure 22 is a bottom plan view of the luminaire mounting interface of Figure 17;Figure 23 is a rear elevation view of the luminaire mounting interface of Figure 17; andFigure 24 is a plan view of the mounting interface of the luminaire mounting interface of Figure 17.The portions in dashed lines do not form part of the design.