boards: add adc support for gd32 boards

This add adc support for gd32f350r_eval, gd32f450i_eval and
gd32vf103v_eval boards.

Signed-off-by: HaiLong Yang <hailong.yang@brainco.cn>

boards/arm/gd32f350r_eval/doc/index.rst

@@ -62,6 +62,9 @@ The board configuration supports the following hardware features:
    * - PINMUX
      - :kconfig:option:`CONFIG_PINCTRL`
      - :dtcompatible:`gd,gd32-pinctrl-af`
+   * - ADC
+     - :kconfig:option:`CONFIG_ADC`
+     - :dtcompatible:`gd,gd32-adc`
 
 Serial Port
 ===========

boards/arm/gd32f350r_eval/gd32f350r_eval-pinctrl.dtsi

@@ -11,4 +11,10 @@
 			pinmux = <USART0_TX_PA9>, <USART0_RX_PA10>;
 		};
 	};
+
+	adc0_default: adc0_default {
+		group1 {
+			pinmux = <ADC_IN11_PC1>;
+		};
+	};
 };

boards/arm/gd32f350r_eval/gd32f350r_eval.dts

@@ -26,3 +26,11 @@
 	pinctrl-0 = <&usart0_default>;
 	pinctrl-names = "default";
 };
+
+&adc0 {
+	status = "okay";
+	/* Set ADC0 clock source to RCU_ADCCK_APB2_DIV4. */
+	rcu-clock-source = <4>;
+	pinctrl-0 = <&adc0_default>;
+	pinctrl-names = "default";
+};

boards/arm/gd32f403z_eval/doc/index.rst

@@ -72,7 +72,8 @@ The board configuration supports the following hardware features:
 +-----------+------------+-----------------------+
 | UART      | on-chip    | serial port-polling   |
 +-----------+------------+-----------------------+
-
+| ADC       | on-chip    | ADC                   |
++-----------+------------+-----------------------+
 
 Serial Port
 ===========

boards/arm/gd32f403z_eval/gd32f403z_eval-pinctrl.dtsi

@@ -12,6 +12,12 @@
 		};
 	};
 
+	adc0_default: adc0_default {
+		group1 {
+			pinmux = <ADC012_IN13_PC3>;
+		};
+	};
+
 	pwm0_default: pwm0_default {
 		group1 {
 			pinmux = <TIMER0_CH0_PA8_OUT_NORMP>;

boards/arm/gd32f403z_eval/gd32f403z_eval.dts

@@ -88,6 +88,12 @@
 	status = "okay";
 };
 
+&adc0 {
+	status = "okay";
+	pinctrl-0 = <&adc0_default>;
+	pinctrl-names = "default";
+};
+
 &usart0 {
 	status = "okay";
 	current-speed = <115200>;

boards/arm/gd32f450i_eval/doc/index.rst

@@ -86,6 +86,9 @@ The board configuration supports the following hardware features:
    * - EEPROM
      - :kconfig:option:`CONFIG_EEPROM`
      - :dtcompatible:`atmel,at24`
+   * - ADC
+     - :kconfig:option:`CONFIG_ADC`
+     - :dtcompatible:`gd,gd32-adc`
 
 Serial Port
 ===========

boards/arm/gd32f450i_eval/gd32f450i_eval-pinctrl.dtsi

@@ -12,6 +12,12 @@
 		};
 	};
 
+	adc0_default: adc0_default {
+		group1 {
+			pinmux = <ADC012_IN13_PC3>;
+		};
+	};
+
 	dac_default: dac_default {
 		group1 {
 			pinmux = <DAC_OUT0_PA4>;

boards/arm/gd32f450i_eval/gd32f450i_eval.dts

@@ -104,6 +104,12 @@
 	pinctrl-names = "default";
 };
 
+&adc0 {
+	status = "okay";
+	pinctrl-0 = <&adc0_default>;
+	pinctrl-names = "default";
+};
+
 &dac {
 	status = "okay";
 	pinctrl-0 = <&dac_default>;

boards/riscv/gd32vf103v_eval/doc/index.rst

@@ -67,6 +67,9 @@ The board configuration supports the following hardware features:
    * - USART
      - :kconfig:option:`CONFIG_SERIAL`
      - :dtcompatible:`gd,gd32-usart`
+   * - ADC
+     - :kconfig:option:`CONFIG_ADC`
+     - :dtcompatible:`gd,gd32-adc`
 
 Serial Port
 ===========

boards/riscv/gd32vf103v_eval/gd32vf103v_eval-pinctrl.dtsi

@@ -30,4 +30,10 @@
 				 <SPI0_MISO_PA6_OUT_NORMP>;
 		};
 	};
+
+	adc0_default: adc0_default {
+		group1 {
+			pinmux = <ADC01_IN13_PC3>;
+		};
+	};
 };

boards/riscv/gd32vf103v_eval/gd32vf103v_eval.dts

@@ -137,3 +137,9 @@
 		jedec-id = [c8 40 15];
 	};
 };
+
+&adc0 {
+	status = "okay";
+	pinctrl-0 = <&adc0_default>;
+	pinctrl-names = "default";
+};