@ning exact, the OSD scaler is shared between the OSD1 & OSD1, but we use the scaler to update automatically the field when in interlace mode, if we wanted to enable OSD2 we should switch the field manually in the vsync irq. It's doable but I don't plan on doing it
For A311D, Amlogic did a brand new blender module for OSD and VD planes, but I don't have the exact capabilities of the blender and the number of available scalers, when I'll have the info, I may expose more OSD planes and eventually a Cursor plane.