EC20 driver installation on RaspberryPi

Hi, I have a problem installing the driver for EC20 on my raspberry pi. I have written the .c files needed but they cannot be compiled and build to .ko file.

currently, I use the base kernel from
and the custom .c files are in
The custom .c files then copied to the respective file in the base kernel folder.

i use this code to compile
make -C /lib/modules/uname -r/build M=pwd/drivers/usb.serial obj-m=option.ko modules
but it return ‘No rule to make target modules’

Check the Makefile .