Thanks Rob. One question on setting "minItems: ". Please see below. >> +allOf: >> + - if: >> + properties: >> + compatible: >> + contains: >> + enum: >> + - nvidia,tegra194-smmu >> + then: >> + properties: >> + reg: >> + minItems: 2 >> + maxItems: 2 >This doesn't work. The main part of the schema already said there's only >1 reg region. This part is ANDed with that, not an override. You need to add an else clause with 'maxItems: 1' and change the base schema to >{minItems: 1, maxItems: 2}. As the earlier version of base schema doesn't have "minItems: " set, should it be set to 0 for backward compatibility? Or can it just be omitted setting in base schema as before? "else" part to set "maxItems: 1" and setting "maxItems: 2" in base schema is clear to me. -KR