riscv + sbi_serial + mtd-ram

Hi,

I am currently working on a riscv platform that: 1) uses the sbi putchar / getchar as serial. 2) maps its `flash` directly to ram as `mtd-ram`[1] (snippet from device tree provided by the ROM, forwarded by OpenSBI).

I successfully implemented 1) based on other serial drivers. But I would like advice on point 2). The IO part should be straightforward, just forwarding reads and writes to the ram is enough. I am having a hard time figuring out the plumbing (where should I implement these functions).

Any thoughts would be appreciated.

Best, Marcelo

[1] ``` flash@8000000000000000 { #address-cells = <0x02>; #size-cells = <0x02>; compatible = "mtd-ram"; bank-width = <0x04>; reg = <0x80000000 0x00 0x00 0x3c00000>; linux,mtd-name = "flash.0"; }; ```