ESP32-S3: Add RtcI2c driver (#4016)

* ESP32-S3: Add RtcI2c driver

* limit cfg

* un-hide traits

* fix macro and doc

* Document driver

* fix doc

* Add HIL test

* use builder lite for timings

* no-const

* review comments

Author: Dominaezzz

esp-hal/CHANGELOG.md

@@ -25,6 +25,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Expose cache line configuration (#3946)
 - ESP32: Expose `psram_vaddr_mode` via `PsramConfig` (#3990)
 - ESP32-S3: Expose more `Camera` config options (#3996)
+- ESP32-S3: Add RtcI2c driver (#0000)
 - `ShaBackend, Sha<N>Context`: Work-queue based SHA driver (#4013)
 - I2S: `i2s::master::Config` with support for more TDM mode standards (#3985)
 

esp-hal/src/gpio/mod.rs

@@ -357,6 +357,9 @@ pub enum RtcFunction {
     Rtc     = 0,
     /// Digital mode.
     Digital = 1,
+    /// RTC_I2C mode.
+    #[cfg(soc_has_rtc_i2c)]
+    I2c     = 3,
 }
 
 /// Trait implemented by RTC pins

esp-hal/src/i2c/mod.rs

@@ -14,3 +14,9 @@ pub mod master;
 crate::unstable_module! {
     pub mod lp_i2c;
 }
+
+#[cfg(esp32s3)] // Only support ESP32-S3 for now.
+#[cfg(soc_has_rtc_i2c)]
+crate::unstable_module! {
+    pub mod rtc;
+}