[TEST] Add MCU list in RTC automated test

[toyowata]

• Add "mcu" key with lists of RTC support targets (#define DEVICE_RTC 1
  in device.h), now MBED_16 test is not executed by non-RTC targets

[0xc0170]

This fixes it ,however we should think about something more maintainable.

Isn't there a way for singletest to find out if that test is supported or not, besides #error message. I'll speak to @PrzemekWirkus.

[PrzemekWirkus]

There are few options here:

1. Use #if DEVICE_RTC in RTC's test case C/C++ source code to make sure we are calling RTC procedures only when RTC is there. If no RTC return new test result value like SKIPPED etc.
   We would have to add new test case result, e.g. RESULT_NO_SUPPORT and e.g. assume test will be compiled and flashed but instead of test execution we will just return to test environment 'that test is skipper / not supported for this platform'.
2. Add RTC as peripheral so it will join peripherals family together with 'ethernet', digital_loop, TMP102 or port_loop.
   Problem here: we would have to update RTC test case with peripheral marker and add to all targets with RTC new property :/
3. Leave it as it is, RTC will just fail on platforms without RTC and we will ignore this 'FAIL's.

PS: @toyowata - sorry I can't give you 👍 here, this should be discussed a bit and we should make this a scalable solution. Today RTC, tomorrow other peripheral may be excluded from platform. I do not want to maintain long list of MCUs supporting RTC. It just creates technical debt in workspace_tools.

[Sissors]

While I think number 1 would be an easy and adequate solution, other options:

1. Use an external RTC for those which have no RTC. The mbed code allows for external RTC to be used for your internal time. Downside is of course you have another external device required.
2. Automatically create a list of targets which support RTC and use that to determine if they test is excecuted, instead of the manual list here. For something I am looking at I do now have python code which automatically can create a list of targets which have a certain peripheral, so something like that could be used to automate it before running the tests.

[star297]

More importantly, if a MCU has a separately backed up RTC could we ensure this works and does not get reset on power down or MCU reset. NXP and Freescale targets appear to have this correctly configured, whereas non of the ST targets I have work correctly and SiLabs Gecko's have the same problem at the moment, however I believe this on the to-do list.

[bridadan]

I think adding RTC to the peripherals list is the most scalable option discussed so far. It wouldn't take much time to add the RTC peripheral for each platform (@toyowata has done the hard part already and figured out which platforms support RTC) and whoever adds a new platform will be responsible for adding the peripheral.

[toyowata]

All,

All, than you very much for suggestions. I agreed that there should be the peripheral list for RTC targets and automated test MBED_16 should be tested only RTC enabled targets.

I will close this PR.