doc: posix: mark posix signals supported with undefined behaviour
posix: add stubs for signal.h functions that need process support
posix: procN: add missing alias for getpid()
scripts: ci: guideline_check: mitigate excessive false positives
tests: posix: one tier0 platform per arch for integration tests
doc: fix code samples in dns_sd documentation so that they compile
tests: net: mqtt: Make publisher/subscriber test suites self contained
tests: net: mqtt: Group existing MQTT 3.1.1 test suites