## Kconfig Symbol Enablement

Three Kconfig symbols need to be enabled for this feature to work, namely `RETAINED_MEM`, `RETENTION`, and `RETENTION_BOOT_MODE`. Typically, this is done by `imply`ing the symbols for the board symbol in the `Kconfig.<board>`, file, e.g.:

```dts
config BOARD_TOFU65
    select SOC_RP2040
    imply RETAINED_MEM
    imply RETENTION
    imply RETENTION_BOOT_MODE
```

By using `imply` at the board level, users of the board can choose to override the setting and disable the feature if they so choose.
