If the only difference between ST7735S and ST7735R is the resolution (128x64 instead of 128x160), then you may be able to use fbcp-ili9341 to drive the display, by changing this line https://github.com/juj/fbcp-ili9341/blo ... 735r.h#L23
to do 64 instead of 160. See https://github.com/juj/fbcp-ili9341
If there are other differences between the two, then fbcp-ili9341 probably does not apply (and may be a waste of time). In that case, try searching the web for driver code or libraries from projects that have successfully used ST7735S, and/or try to find the spec sheet to see if you can develop or port a driver for it.