Are there software tools to draw high level block diagrams for chips?
Is there a standard for such symbols or people draw these things by hand?


For a lot of things in flow charts, there are standards; it depends from the context, for most:

For example, there's a rich canon of standards symbols from signal processing and control theory, for example for low-pass filters, for error detectors, oscillators, etc.

Data processing has its own types of diagrams - with symbols for memory, processes, data transformations...

Same applies to chemical processing, motor control, climate control...

So, yes, there's standards, but they typically arise from the application field the user of an IC might be versed in.