Early console using RISC-V SBI

modulename: earlycon-riscv-sbi.ko

configname: CONFIG_SERIAL_EARLYCON_RISCV_SBI

Linux Kernel Configuration
└─>Device Drivers
└─>Character devices
└─>Serial drivers
└─>Early console using RISC-V SBI
In linux kernel since version 5 (release Date: 2019-03-03)  
Support for early debug console using RISC-V SBI. This enables
the console before standard serial driver is probed. This is enabled
with "earlycon=sbi" on the kernel command line. The console is
enabled when early_param is processed.

source code:
drivers/tty/serial/earlycon-riscv-sbi.c