Writing Arm64 Assembly for #PinePhone 😬
https://github.com/lupyuen/incubator-nuttx/blob/pinephone/arch/arm64/src/qemu/qemu_lowputc.S#L74-L89
And why we're doing #PinePhone UART in Arm64 Assembly
https://lupyuen.github.io/articles/uboot?89#nuttx-uart-macros