Ambiq RTC differences

[RichardSWheatley]

Hello, @bjarki-trackunit!

You are the maintainer for the RTC section.
I am writing the Ambiq RTC driver when I noticed that the tests for RTC make some assumptions that are not true for the Ambiq RTC.

1. We do not support 99-00 rollover which I already fixed in the tests by adding a check for EINVAL.

	if (ret == -EINVAL) {
		TC_PRINT("Rollover not supported\n");
		ztest_test_skip();
	} else {
		zassert_ok(ret, "RTC Set Time Failed");
	}

2. When setting the alarms, for the Ambiq RTC you must set the entire struct with a non-zero value

This makes our implementation fail the most of the testing without additions to the tests.
I do not like to make additions to tests unless it is absolutely needed.

Do you think there is a better way to accomplish this?

[bjarki-trackunit]

Regarding issue 1, returning -EINVAL is the correct behavior, and skipping the test if -EINVAL is returned is appropriate.

Regarding issue 2, the test suite can be updated to set every supported field, rather than just hours and minutes. This is a valid configuration which should be supported by all RTCs.

We can add an additional test to validate that only the selected alarm time fields are used, which is a valid configuration for most RTCs, this test can be skipped if the RTC returns -EINVAL, which would be the case for the AMBIQ RTC.

[RichardSWheatley]

Thank you! I will create a draft pull request for this and you can check my implementation.