句中of的用法是什么？语法上如何解析？

主干结构A is B, not C

C = {what is advocated by a small number of countries of the so-called“rules-based” international order}

of作为功能词表示前后两个名词结构同位[1]，即

what is advocated by a small number of countries = the so-called “rules-based international order”

少数几个国家所鼓吹的东西 = 所谓的“基于规则的国际秩序”

这个句子大概率并非出自英语母语人士之手，因为这里的of同位有些勉强（前者名词性从句，后者名词）；加之主干结构需要C与B尽可能对称；第三，A已经用了what句式，其后加以肯定说明或否定的也是what句式，不够清晰。可修改如下

What China and the international community follow and uphold is the United Nations-centered international system and international order underpinned by international law, not the so-called "rules-based" international order advocated by a small number of countries.

B与C都是名词+后置定语（过去分词短语）

中文（大意）：

中国与国际社会所遵循并捍卫是以国际法为基石以联合国为中心的国际体系与秩序，而非少数几个国家鼓吹的所谓“基于规则”的国际秩序。

注1：follow or upload中的or不妥当，表示并列（可选）时可以，这里明显有递进，只能用and.

注2：即便如此，仍然累赘，精简如下。意思不变，结构更为对称：

What China and the international community follow and uphold is the United Nations-centered international order underpinned by international laws, not the so-called "rules-based" one advocated by a small number of countries.

当然更简明的是把主干的what主语从句与is部分合并在一起，也不代表"international community"，表明自己态度即可：

China follows and upholds the United Nations-centered international order underpinned by international laws, not the so-called "rules-based" one advocated by a small number of countries.