bhnd_retain_provider
pmu_dev = bhnd_retain_provider(child, BHND_SERVICE_PMU);
nvram = bhnd_retain_provider(child, BHND_SERVICE_NVRAM);
sc->chipc_dev = bhnd_retain_provider(dev, BHND_SERVICE_CHIPC);
chipc = bhnd_retain_provider(child, BHND_SERVICE_CHIPC);
pwrctl = bhnd_retain_provider(child, BHND_SERVICE_PWRCTL);
sc->sc_chipc = bhnd_retain_provider(sc->sc_dev, BHND_SERVICE_CHIPC);
sc->sc_gpio = bhnd_retain_provider(sc->sc_dev, BHND_SERVICE_GPIO);
sc->sc_pmu = bhnd_retain_provider(sc->sc_dev, BHND_SERVICE_PMU);