Ochna serrulata (Mickey Mouse Plant). The sepals will later turn bright red, and the berries dark, extending the show. It is one of my favorite shrubs, and super easy from seed. But they are very slow growing, especially when young.

They're actually Ochna integerrima. Vietnamese celebrate Tết (lunar new year) with branches of mai vàng (O integerrima). O serrulata would have a red calyx.

From my understanding, Ochna integerrima (aka O. thomasiana) has wider leaves. The downward hanging flowers are also indicative of O. serrulata. The reddening of the sepals come later, after the flowers. Following are two pictures of the same O. serrulata shrub.

GF, you're right by pointing out the down facing flowers. I stand corrected. The O integerrima tend to have upturn blossoms.