An MTK driver is not a single file but a suite of kernel modules responsible for managing diverse peripherals: GPIO, I2C, SPI, UART, display (DSI/DPI), camera (CSI/ISP), audio (I2S/TDM), Wi-Fi/BT combo chips, and power management (PMIC). Architecturally, these drivers follow the standard Linux device model, but with a distinct MediaTek flavor.
The most critical drivers for "flashing" a device. They allow the computer to communicate with the phone while it is powered off or in a pre-loader state. mtk drivers