drivers: rtc: set 'rtc_driver_api' as 'static const'

This change marks each instance of the 'rtc_driver_api' as 'static const'.
The rationale is that 'rtc_driver_api' is used for declaring internal
module interfaces and is not intended to be modified at runtime.
By using 'static const', we ensure immutability, leading to usage of only
.rodata and a reduction in the .data area.

Signed-off-by: Pisit Sawangvonganan <[email protected]>

Author: ndrs-pst

drivers/rtc/rtc_emul.c

@@ -461,7 +461,7 @@ static int rtc_emul_get_calibration(const struct device *dev, int32_t *calibrati
 }
 #endif /* CONFIG_RTC_CALIBRATION */
 
-struct rtc_driver_api rtc_emul_driver_api = {
+static const struct rtc_driver_api rtc_emul_driver_api = {
 	.set_time = rtc_emul_set_time,
 	.get_time = rtc_emul_get_time,
 #ifdef CONFIG_RTC_ALARM

drivers/rtc/rtc_fake.c

@@ -70,7 +70,7 @@ static void fake_rtc_reset_rule_before(const struct ztest_unit_test *test, void
 ZTEST_RULE(fake_rtc_reset_rule, fake_rtc_reset_rule_before, NULL);
 #endif /* CONFIG_ZTEST */
 
-struct rtc_driver_api rtc_fake_driver_api = {
+static const struct rtc_driver_api rtc_fake_driver_api = {
 	.set_time = rtc_fake_set_time,
 	.get_time = rtc_fake_get_time,
 #ifdef CONFIG_RTC_ALARM

drivers/rtc/rtc_ll_stm32.c

@@ -390,7 +390,7 @@ static int rtc_stm32_get_calibration(const struct device *dev, int32_t *calibrat
 #endif
 #endif /* CONFIG_RTC_CALIBRATION */
 
-struct rtc_driver_api rtc_stm32_driver_api = {
+static const struct rtc_driver_api rtc_stm32_driver_api = {
 	.set_time = rtc_stm32_set_time,
 	.get_time = rtc_stm32_get_time,
 	/* RTC_ALARM not supported */

drivers/rtc/rtc_mc146818.c

@@ -495,7 +495,7 @@ static void rtc_mc146818_isr(const struct device *dev)
 #endif
 }
 
-struct rtc_driver_api rtc_mc146818_driver_api = {
+static const struct rtc_driver_api rtc_mc146818_driver_api = {
 	.set_time = rtc_mc146818_set_time,
 	.get_time = rtc_mc146818_get_time,
 #if defined(CONFIG_RTC_ALARM)

drivers/rtc/rtc_sam.c

@@ -645,7 +645,7 @@ static int rtc_sam_get_calibration(const struct device *dev, int32_t *calibratio
 }
 #endif /* CONFIG_RTC_CALIBRATION */
 
-static struct rtc_driver_api rtc_sam_driver_api = {
+static const struct rtc_driver_api rtc_sam_driver_api = {
 	.set_time = rtc_sam_set_time,
 	.get_time = rtc_sam_get_time,
 #ifdef CONFIG_RTC_ALARM

drivers/rtc/rtc_smartbond.c

@@ -561,7 +561,7 @@ static int rtc_smartbond_update_set_callback(const struct device *dev, rtc_updat
 }
 #endif
 
-struct rtc_driver_api rtc_smartbond_driver_api = {
+static const struct rtc_driver_api rtc_smartbond_driver_api = {
 	.get_time = rtc_smartbond_get_time,
 	.set_time = rtc_smartbond_set_time,
 #if defined(CONFIG_RTC_ALARM)