Re: [PATCH v5 2/2] watchdog: Add new arm_smc_wdt watchdog driver

[Julius Werner]

> +       err = of_property_read_u32(pdev->dev.of_node, "arm,smc-id",
> +                                  &smc_func_id);
> +       if (err < 0)
> +               return err;
> +       watchdog_set_drvdata(wdd, (void *)(uintptr_t)smc_func_id);

Your device tree binding says there's a default and this is optional.
I think you need to change the code so that that's actually true.