esp32: dts: add RTC timer node

- add RTC timer node bindings
- add RTC timer node to the DT.

Signed-off-by: Glauber Maroto Ferreira <glauber.ferreira@espressif.com>

dts/bindings/counter/espressif,esp32-rtc-timer.yaml

@@ -0,0 +1,25 @@
+# Copyright (c) 2022 Espressif Systems (Shanghai) Co., Ltd.
+# SPDX-License-Identifier: Apache-2.0
+
+description: |
+
+        Espressif's Counter Driver based on RTC Main Timer.
+
+        Any reset/sleep mode, except for the power-up reset, will not
+        stop or reset the RTC Timer. This behavior may be handy when
+        supporting applications that need to keep a timing baseline on
+        such situations.
+
+        There is also no need to enable the RTC Timer node, it starts
+        running from power-up.
+
+include: base.yaml
+
+properties:
+    slow-clk-freq:
+      description: |
+        The slow clock input frequency for the RTC Timer.
+      type: int
+      required: true
+
+compatible: "espressif,esp32-rtc-timer"

dts/riscv/espressif/esp32c3.dtsi

@@ -68,7 +68,15 @@
 			reg = <0x60008000 0x1000>;
 			xtal-freq = <ESP32_CLK_XTAL_40M>;
 			#clock-cells = <1>;
-			status = "ok";
+			status = "okay";
+
+			rtc_timer: rtc_timer {
+				compatible = "espressif,esp32-rtc-timer";
+				slow-clk-freq = <ESP32_RTC_SLOW_CLK_FREQ_90K>;
+				interrupts = <RTC_CORE_INTR_SOURCE>;
+				interrupt-parent = <&intc>;
+				status = "okay";
+			};
 		};
 
 		flash: flash-controller@60002000 {

dts/xtensa/espressif/esp32.dtsi

@@ -65,7 +65,15 @@
 			reg = <0x3ff48000 0x0D8>;
 			xtal-freq = <ESP32_CLK_XTAL_40M>;
 			#clock-cells = <1>;
-			status = "ok";
+			status = "okay";
+
+			rtc_timer: rtc_timer {
+				compatible = "espressif,esp32-rtc-timer";
+				slow-clk-freq = <ESP32_RTC_SLOW_CLK_FREQ_150K>;
+				interrupts = <RTC_CORE_INTR_SOURCE>;
+				interrupt-parent = <&intc>;
+				status = "okay";
+			};
 		};
 
 		flash: flash-controller@3ff42000 {

dts/xtensa/espressif/esp32s2.dtsi

@@ -65,7 +65,15 @@
 			reg = <0x3f408000 0x0D8>;
 			xtal-freq = <ESP32_CLK_XTAL_40M>;
 			#clock-cells = <1>;
-			status = "ok";
+			status = "okay";
+
+			rtc_timer: rtc_timer {
+				compatible = "espressif,esp32-rtc-timer";
+				slow-clk-freq = <ESP32_RTC_SLOW_CLK_FREQ_90K>;
+				interrupts = <RTC_CORE_INTR_SOURCE>;
+				interrupt-parent = <&intc>;
+				status = "okay";
+			};
 		};
 
 		flash: flash-controller@3f402000 {