You don't use the definite article when talking about companies/brands. However, you do use it when talking about products, because in those instances, you're using the brand name as an adjective. If you're talking about "the Huawei phone", the noun is "phone", so it follows the normal rules of grammar. The only difference is that you're using the company name as a modifier, but this doesn't affect the grammar.
Apple products are a bit different, because they often are the nouns themselves. You don't need to say "the iPhone phone". However, I would argue that the "i" in this instance is the modifier. Apple often uses the noun in the name of the item itself. A clearer example is "Apple Watch", where the brand name is clearly the modifier, and "Watch" is the noun. This is just a marketing strategy, but again, it doesn't affect the grammar.
Which watch is it? It's the Apple Watch.
Which phone is it? It's the iPhone.