It's the lowest possible effort custom design you could make. The only major difference between the three generations of Pi SoCs (BCM2835, 2836, 2837) is the CP

It's the lowest possible effort custom design you could make. The only major difference between the three generations of Pi SoCs (BCM2835, 2836, 2837) is the CPU, so it's a 5 year old SoC designed for set top boxes with a single IP block swapped out.