His mother:主语
is waiting for him 谓语 （由动词和介词短语构成）
outside 地点状语你能把is waiting for him中具体分析一下吗？is waiting 现在进行时 动词
for 介词
him 人称代词宾格，做for的介词宾语
for him 介词短语 与is waiting搭配因为wait是不及物动词，需要后面有介词短语