Missing driver: FocalTech FT3658U not found in kernel modules source

[slakkystar]

Device: OPPO Reno 11F (OP5A0BL1 / CPH2603)
Branch: oppo/mt6877_u_14.0.1_reno11_f_5g
Kernel version: 4.19

Issue:
The stock defconfig (k6877v1_64_k419_defconfig) enables:CONFIG_TOUCHPANEL_FOCAL_FT3658U=y

However, the corresponding Kconfig and driver source code are missing from the published kernel source.As I understand it, drivers from other branches won't work for it. I think it has its own device-specific changes.

Request:
Could you please provide the missing source files for the FocalTech FT3658U touchscreen driver?

Thank you.