SAM0: Inability to configure ADC for internal temperature sensor

[toshbi4]

Controller: SamL21 (samr34j18b)

Problem:
Following this condition in SAM0 ADC driver (https://github.com/zephyrproject-rtos/zephyr/blob/main/drivers/adc/adc_sam0.c#L462) we can initialize ADC driver only with the corresponding controller's pins.
However, internal ADC temperature measurement in SUPC isn't provided with any controller's pins.
Hence, we can't use this ADC driver for reading ADC values with internal temperature measurements.

Testing:
A simple and direct solution - to comment out this condition (pinctrl checking) - made a success, so it means that it is redundant for this particular case...

Do somebody know maybe there are better ways to deal with it, or it looks like bug and should be fixed?)

Link to SAM documentation about internal temperature sensor (page 947, "Device Temperature Measurement"):
https://ww1.microchip.com/downloads/en/DeviceDoc/SAM_L21_Family_DataSheet_DS60001477C.pdf

[toshbi4]

To avoid triggering this condition you can just create empty pinctrl definition.
For example:

pinctrl.dtsi

adc_pins_default: adc_pins_default {
    };

overlay.dts

&adc {
	label = "ADC_TEMP";
	status = "okay";
	pinctrl-0 = <&adc_pins_default>;
	pinctrl-names = "default";
};